* add usage arguments to get_key_byname or return a PKC_LIST with
      all keys and add a selection.

    * add readline support. Must enhance libreadline - Anyone?

    * Burn the buffers used by fopen(), or use read(2).

    * enable a SIGSEGV handler while using zlib functions

    * improve iobuf by reading more than one byte at once,
      this shoud espceially done for the buffer in the chain.
      Change the buffering to a mbuf like scheme? Need it for PSST anyway.
    * add a way to distinguish between errors and eof in the underflow/flush
      function of iobuf.
    * add checking of armor trailers
    * remove all "Fixmes"


    * bug: g10/trustdb.c#build_sigrecs called to often by do_list_path
      and remove the bad kludge. Maybe we should put all sigs into the trustdb
      and mark them as valid/invalid/nopubkey, and how do we check, that
      we have a self-signature -> put this stuff into a kind of directory
      record, as it does not belong to the pubkey record?

    * add an option to create a new user id.
      Make it possible to change the signature class of the self-signatures,
      which can then be used to change the displayed order of user-ids:
      Put the user-id with a self-signature of class 0x13 always on top
      of the displayed list (needs changes in the user-id-from-keyid
      functions).

    * enhance --sign-key, so that multiple-user-ids can be signed
      (use the new classes 0x14..17), partly implemented, but I think we
      should better make use of notation data - for now we allow only one
      user id.

    * add an option to re-create a public key from a secret key. Think about
      a backup system of only the secret part of the secret key.

    * add fingerprint/keyid hashing. We need a new field in PKC to
      flag that we may have a cached signature for this (and use the address
      of PKC to lookup the hash).

    * change the misleading usage of "public key certificate" to
      "public key data" or something like this.

    * replace getkey.c#enum_secret_keys