[#3256] fix common warnings across compilers

```
io_service_thread_pool_unittests.cc:24:12: warning: unused variable 'TEST_TIMEOUT' [-Wunused-const-variable]
mysql_connection_unittest.cc:217:75: warning: declaration of ‘out_bindings’ shadows a previous local [-Wshadow]
mysql_host_data_source.cc:171:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:202:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:220:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:254:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:422:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:554:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:579:30: warning: useless cast to type ‘isc::dhcp::SubnetID’ {aka ‘unsigned int’} [-Wuseless-cast]
mysql_host_data_source.cc:586:30: warning: useless cast to type ‘isc::dhcp::SubnetID’ {aka ‘unsigned int’} [-Wuseless-cast]
mysql_host_data_source.cc:674:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:714:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:1313:18: warning: 'processFetchedData' overrides a member function but is not marked 'override' [-Wsuggest-override]
mysql_host_data_source.cc:1353:37: warning: 'createBindForReceive' overrides a member function but is not marked 'override' [-Wsuggest-override]
mysql_host_data_source.cc:1371:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:1456:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:1487:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:1508:18: warning: 'processFetchedData' overrides a member function but is not marked 'override' [-Wsuggest-override]
mysql_host_data_source.cc:1542:37: warning: 'createBindForReceive' overrides a member function but is not marked 'override' [-Wsuggest-override]
mysql_host_data_source.cc:1583:6: warning: extra ';' after member function definition [-Wextra-semi]
mysql_host_data_source.cc:1803:25: warning: unused variable 'OPTION_ID_COL' [-Wunused-const-variable]
mysql_host_data_source.cc:1804:25: warning: unused variable 'CODE_COL' [-Wunused-const-variable]
mysql_host_data_source.cc:1805:25: warning: unused variable 'VALUE_COL' [-Wunused-const-variable]
mysql_host_data_source.cc:1806:25: warning: unused variable 'FORMATTED_VALUE_COL' [-Wunused-const-variable]
mysql_host_data_source.cc:1807:25: warning: unused variable 'SPACE_COL' [-Wunused-const-variable]
mysql_host_data_source.cc:1808:25: warning: unused variable 'PERSISTENT_COL' [-Wunused-const-variable]
mysql_host_data_source.cc:1809:25: warning: unused variable 'CANCELLED_COL' [-Wunused-const-variable]
mysql_host_data_source.cc:1810:25: warning: unused variable 'USER_CONTEXT_COL' [-Wunused-const-variable]
mysql_host_data_source.cc:1811:25: warning: unused variable 'DHCP_SUBNET_ID_COL' [-Wunused-const-variable]
mysql_host_data_source.cc:1812:25: warning: unused variable 'HOST_ID_COL' [-Wunused-const-variable]
mysql_host_data_source.cc:3222:24: warning: useless cast to type ‘char*’ [-Wuseless-cast]
mysql_host_data_source.cc:3385:24: warning: useless cast to type ‘char*’ [-Wuseless-cast]
mysql_host_data_source.cc:3426:24: warning: useless cast to type ‘char*’ [-Wuseless-cast]
mysql_lease_mgr.cc:89:14: warning: unused variable 'HOSTNAME_MAX_LEN' [-Wunused-const-variable]
mysql_lease_mgr.cc:95:14: warning: unused variable 'ADDRESS6_TEXT_MAX_LEN' [-Wunused-const-variable]
mysql_lease_mgr.cc:98:14: warning: unused variable 'USER_CONTEXT_MAX_LEN' [-Wunused-const-variable]
mysql_lease_mgr.cc:544:29: warning: useless cast to type ‘isc::db::my_bool*’ {aka ‘bool*’} [-Wuseless-cast]
mysql_lease_mgr.cc:1929:10: warning: 'start' overrides a member function but is not marked 'override' [-Wsuggest-override]
mysql_lease_mgr.cc:2010:30: warning: useless cast to type ‘isc::dhcp::SubnetID’ {aka ‘unsigned int’} [-Wuseless-cast]
mysql_lease_mgr.cc:2020:10: warning: 'getNextRow' overrides a member function but is not marked 'override' [-Wsuggest-override]
mysql_lease_mgr.cc:3427:13: warning: useless cast to type ‘uint64_t’ {aka ‘long unsigned int’} [-Wuseless-cast]
mysql_lease_mgr.cc:4114:23: warning: variable length arrays are a C99 feature [-Wvla-extension]
mysql_lease_mgr.cc:4226:23: warning: variable length arrays are a C99 feature [-Wvla-extension]
option_opaque_data_tuples_unittest.cc:533:32: warning: zero size arrays are an extension [-Wzero-length-array]
option_opaque_data_tuples_unittest.cc:552:32: warning: zero size arrays are an extension [-Wzero-length-array]
option_opaque_data_tuples_unittest.cc:572:32: warning: zero size arrays are an extension [-Wzero-length-array]
tcp_connection.cc:28:14: warning: unused variable 'MAX_LOGGED_MESSAGE_SIZE' [-Wunused-const-variable]
test_control.cc:1826:23: warning: useless cast to type ‘class isc::asiolink::IOAddress’ [-Wuseless-cast]
test_control.cc:1830:24: warning: useless cast to type ‘class isc::asiolink::IOAddress’ [-Wuseless-cast]
test_control.cc:1871:34: warning: useless cast to type ‘class isc::asiolink::IOAddress’ [-Wuseless-cast]
test_control.cc:1873:30: warning: useless cast to type ‘class isc::asiolink::IOAddress’ [-Wuseless-cast]
../../../src/lib/http/http_message_parser_base.h:26:45: warning: extra ‘;’ after in-class function definition [-Wextra-semi]
../../../src/lib/http/http_message_parser_base.h:174:18: warning: ‘virtual void isc::http::HttpMessageParserBase::defineEvents()’ can be marked override [-Wsuggest-override]
../../../src/lib/http/http_message_parser_base.h:177:18: warning: ‘virtual void isc::http::HttpMessageParserBase::verifyEvents()’ can be marked override [-Wsuggest-override]
../../../src/lib/http/http_message_parser_base.h:180:18: warning: ‘virtual void isc::http::HttpMessageParserBase::defineStates()’ can be marked override [-Wsuggest-override]
../../../src/lib/http/http_message_parser_base.h:233:18: warning: ‘virtual void isc::http::HttpMessageParserBase::onModelFailure(const string&)’ can be marked override [-Wsuggest-override]
```

1 files changed, 13 insertions, 13 deletions

diff --git a/src/lib/mysql/tests/mysql_connection_unittest.cc b/src/lib/mysql/tests/mysql_connection_unittest.cc
index 0591192ab7..c43a20663b 100644
--- a/src/lib/mysql/tests/mysql_connection_unittest.cc
+++ b/src/lib/mysql/tests/mysql_connection_unittest.cc
@@ -214,38 +214,38 @@ public:
         // returned row the lambda provided as 4th argument should be executed.
         ASSERT_NO_THROW_LOG(conn_.selectQuery(MySqlConnectionTest::GET_BY_INT_VALUE,
                                               bindings, out_bindings,
-                                              [&](MySqlBindingCollection& out_bindings) {
+                                              [&](MySqlBindingCollection& captured_out_bindings) {
 
             // Compare received data with input data assuming they are both non-null.
 
-            if (!out_bindings[0]->amNull() && !in_bindings[0]->amNull()) {
+            if (!captured_out_bindings[0]->amNull() && !in_bindings[0]->amNull()) {
                 EXPECT_EQ(static_cast<int>(in_bindings[0]->getInteger<uint8_t>()),
-                          static_cast<int>(out_bindings[0]->getInteger<uint8_t>()));
+                          static_cast<int>(captured_out_bindings[0]->getInteger<uint8_t>()));
             }
 
-            if (!out_bindings[1]->amNull() && !in_bindings[1]->amNull()) {
+            if (!captured_out_bindings[1]->amNull() && !in_bindings[1]->amNull()) {
                 EXPECT_EQ(in_bindings[1]->getInteger<uint32_t>(),
-                          out_bindings[1]->getInteger<uint32_t>());
+                          captured_out_bindings[1]->getInteger<uint32_t>());
             }
 
-            if (!out_bindings[2]->amNull() && !in_bindings[2]->amNull()) {
+            if (!captured_out_bindings[2]->amNull() && !in_bindings[2]->amNull()) {
                 EXPECT_EQ(in_bindings[2]->getInteger<int64_t>(),
-                          out_bindings[2]->getInteger<int64_t>());
+                          captured_out_bindings[2]->getInteger<int64_t>());
             }
 
-            if (!out_bindings[3]->amNull() && !in_bindings[3]->amNull()) {
+            if (!captured_out_bindings[3]->amNull() && !in_bindings[3]->amNull()) {
                 EXPECT_EQ(in_bindings[3]->getString(),
-                          out_bindings[3]->getString());
+                          captured_out_bindings[3]->getString());
             }
 
-            if (!out_bindings[4]->amNull() && !in_bindings[4]->amNull()) {
+            if (!captured_out_bindings[4]->amNull() && !in_bindings[4]->amNull()) {
                 EXPECT_EQ(in_bindings[4]->getBlob(),
-                          out_bindings[4]->getBlob());
+                          captured_out_bindings[4]->getBlob());
             }
 
-            if (!out_bindings[5]->amNull() && !in_bindings[5]->amNull()) {
+            if (!captured_out_bindings[5]->amNull() && !in_bindings[5]->amNull()) {
                 EXPECT_TRUE(in_bindings[5]->getTimestamp() ==
-                            out_bindings[5]->getTimestamp());
+                            captured_out_bindings[5]->getTimestamp());
             }
         }));