Solution: emit socket monitor events for PLAIN protocol errors (like CURVE)

Solution: replaced unreachable code by assertions and adapted uses

Solution: unification, pulled up common behaviour to zap_client_t/zap_client_common_handshake_t

Problem: zap_msg_available duplicated between curve_server_t and plain_server_t (with deviating behaviour)

Solution: pull up into zap_client_common_handshake_t, along with handle_zap_status_code and error_detail/current_error_detail

Solution: extract into new intermediate base class zap_client_common_handshake_t

Solution: pull state enum up to zap_client_t and unify names of enum values

Solution: extract receive_and_process_zap_reply into zap_client_t and convert zap_client_t into base class of the server mechanism classes

Solution: Use zap_client_t::send_zap_request

* Problem: no test case with CURVE encryption and large identity

Solution: added test case (currently crashing)

* Problem: possible buffer overflow in mechanism_t::add_property

Solution: add target buffer length parameter and check the buffer is sufficiently large

* Problem: test cases accidentally excluded from build

Solution: remove #if/#endif

* Problem: possible buffer overruns related to metadata at various locations

Solution: allocate buffer large enough for actual metadata, reduce code duplication

* Problem: syntax error related to pointer type conversion

Solution: change argument type of make_command_with_basic_properties to const char *

* Problem: large metadata may cause an assertion in produce_initiate

Solution: Allow metadata of arbitrary size in produce_initiate

Solution: Define them in zmq.h and use them (currently in DRAFT API)

Solution: if inproc://zeromq.zap.01 exists, which means ZAP is
enabled, abort immediately if it cannot be used (eg: out of memory)
or it is configured incorrectly (eg: wrong socket type).
Otherwise authentication failures will simply be ignored and
unauthorised peers will be allowed to slip in.

Solution: Phase I - make precompiled.hpp be first file included in every source file

Solution: update to 2016

Of course people still "can" distributed the sources under the
LGPLv3. However we provide COPYING.LESSER with additional grants.

Solution: specify these grants in the header of each source file.

Solution: update for 2015

Fixes #1320

- also prioritize ZAP metadata over ZMTP metadata in case application
  uses same names.

- additional messages to help people debugging security errors

The get_credential () member function returns
credential for the last peer we received message for.
The idea is that this function is used to implement user-level API.

* This is passed to the ZAP handler in the 'domain' field

* If not set, or empty, then NULL security does not call the ZAP handler

* This resolves the phantom ZAP request syndrome seen with sockets where
  security was never intended (e.g. in test cases)

* This means if you install a ZAP handler, it will not get any requests
  for new connections until you take some explicit action, which can be
  setting a username/password for PLAIN, a key for CURVE, or the domain
  for NULL.

* Command names changed from null terminated to length-specified
* Command frames use the correct flag (bit 2)
* test_stream acts as test case for command frames
* Some code cleanups

- if ZAP server returns anything except 200, connection is closed
- all security tests now pass correctly
- test_security_curve now does proper client key authentication using test key
- test_security_plain now does proper password authentication

- Split off NULL security check from PLAIN
- Cleaned up test_linger code a little
- Got all tests to pass, added TODOs for outstanding issues
- Added ZAP authentication for NULL test case
- NULL mechanism was not passing server identity - fixed
- cleaned up test_security_plain and removed option double-checks (made code ugly)
- lowered timeout on expect_bounce_fail to 150 msec to speed up checks
- removed all sleeps from test_fork and simplified code (it still passes :-)

This change adds the socket identity infomartion from the socket to the
zap frames.  In doing this the ZAP is able preform different operations
based on different sockets.  This is not compaitable with the current ZAP
RFC, but that can be updated.  As the ZAP rfc is currently draft for I
did not change the version number.

Tests also modified and passing.

RFC23, RFC24, RFC26 now use variable-length command names that
end in null octet (valid C strings) instead of fixed-length
space padded strings.