We use metadata_t directly. No need for generic interface now.

Initialise _has_src_addr variable, fixes hang on Windows.

Added test_metadata

Solution: add this to ZAP reply processing.

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

These commits broke regression tests, so I'm reverting them.

This reverts commit 5e0facda.

This reverts commit 2a84d259.

Broke regression test on test_hwm.cpp.

Feature/divide by zero investigation

These changes cause an assertion in lb_sendpipe() when executing the test_security_plain testcase.

Provides control of race windows and logging for some of the interesting transitions.

Include ZMTP properties in message metadata

Metadata are built in stream_engine now.
This makes it easy to extend metadata with user-defined properties.

Don't add empty metadata to received messages

tweetnacl integration for curve

Conflicts:
	CMakeLists.txt

Add metadata to received messages

Bumped ABI version to 4.0.0

See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=743508

The ABI in fact changed in two significant ways, one with inproc
connects, and one with socket monitoring

Solution: generate libzmq.so.4.0.0 library instead.

This change should be backported to zeromq-4.x

Allow to set up a source address and port for outgoing tcp connections in zmq_connect

Few examples:
tcp:://192.168.0.4:55555;192.168.0.254:1234
tcp:://192.168.0.4:0;192.168.0.254:1234
tcp:://eth2:55555;192.168.0.254:1234

Define i_properties interface

- copy and move message operations are updated to maintain proper
  reference count of properties object
- zmq_msg_gets updated to use i_properties interface to fetch property
  value
- setter/getter added to msg_t class

Update function prototype for zmq_msg_gets ()

Added modifiers reflect the following properties:
- zmq_msg_gets () does not mutate property parameter
- zmq_msg_gets () returns a pointer to memory the caller should not
  modify

Add pointer to properties into message structure

Various small cleanups

- additional messages to help people debugging security errors