[#1736] Initial commit with HA+MT integration

HA+MT fully integrated and functional.

src/hooks/dhcp/high_availability/ha_service.*
    HAService - changed client_ from instance to pointer
              - added listener_

    HAService::startClientAndListener()  - new method which
    instantiates client_ and listener_ instances based on config,
    and starts them

    HAService::stopClientAndListener()  - new method that stops
    client_ and listener_ instances.

    HAService::HAService() - invokes startClientAndListener()

    HAService::~HAService()  - invokes stopClientAndListener()

src/hooks/dhcp/high_availability/tests/Makefile.am
    Added ha_mt_unittest.c

src/hooks/dhcp/high_availability/tests/ha_mt_unittest.cc
    New file with HA+MT related tests

src/hooks/dhcp/high_availability/tests/ha_service_unittest.cc
    Modified tests to ensure use of ST HAService

src/lib/config/cmd_http_listener.h
    Added CmdHttpListener commentary

1 files changed, 12 insertions, 0 deletions

diff --git a/src/lib/config/cmd_http_listener.h b/src/lib/config/cmd_http_listener.h
index a9191bb51e..9473076722 100644
--- a/src/lib/config/cmd_http_listener.h
+++ b/src/lib/config/cmd_http_listener.h
@@ -16,6 +16,18 @@
 namespace isc {
 namespace config {
 
+/// @brief A multi-threaded HTTP listener that can process API commands
+/// requests.
+///
+/// This class will listen for Command API client requests on a given
+/// IP address and port.  It uses its own IOService instance to drive
+/// a thread-pool which can service multiple connections concurrently.  
+/// The number of concurrent connections is currently limited to the
+/// configured thread pool size.
+///
+/// @note This class is NOT compatible with Kea core single-threading.
+/// It is incumbant upon the owner to ensure the Kea core multi-threading
+/// is (or will be) enabled when creating instances of this class.
 class CmdHttpListener {
 public:
     /// @brief Constructor