Fixed the bug which cause the application crashed when use TCP connect to an invalid address(such as 192.168.1.255).

Solution: check/reject a zero routing ID with EINVAL.

These tests connected CLIENT and SERVER to DEALER... this isn't
allowed. I changed to CLIENT-to-SERVER in both cases. The result
was aborts in client.cpp and server.cpp which cannot handle
invalid multipart data.

I removed the asserts in each of these in xsend.

Solution: fix the test cases and remove the (unwanted?) asserts
in client.cpp:xsend and server.cpp:xsend.

It should never be zero.

Solution: if rid cycles back to zero, bump to 1.

This has no sense IMO; people who need this can still use DEALER-DEALER.

Solution: let CLIENT talk only to SERVER.

We do not use 'get' for getters.

Solution: rename to zmq_msg_routing_id () for public API.

Tests were failing, because some deque calls were causing undefined
behavior: calling front() or pop_front() on an empty deque. Such
calls are now safeguarded.

The patch fixes the issue #1568.

The patch fixes lingering subscriptions that occur upon disconnection
on XPUB sockets with option XPUB_MANUAL when used in a XPUB-XSUB
proxies.

Solution: Move the macros to a private header.

-Set signaler_port to 0 which allows the OS to find a free port, rather than crashing if 5905 is in use (https://github.com/zeromq/libzmq/issues/1542)
-Added config.hpp to the source list so it shows up in generated projects
-Remove CMAKE_BUILD_TYPE setting for generators that don't use it

Solution: Convert to spaces and remove trailing whitespace in these files.

Fixes tests that were introduced in a previous pull request. See
https://github.com/zeromq/libzmq/pull/1539#issuecomment-132968987

This patch  adds a new member of type deque to the
xpub class that contains pointers to metadata_t.
This deque is then used (alongside pending_data
and pending_flags) to preserve metadata when
copying messages.

The routing id (identity) frame return when reading from
a router doesn't have the same metadata as the "real"
message that follows.
For example, The ZAP "User-Id" property is missing.

This patch attach the "data message"'s metadata
to the "identity message" when it is read from the router.