Fix failing test case in test_filter_ipc.

Add explicit check for primary group.
Merge pull request #779 from hashstat/master

Fix failing test case in test_filter_ipc.
add test_curve_proxying.cpp
shunt proxy in  test_curve_proxying.cpp
declare correctly the client socket as CURVE and not NULL in  test_curve_proxying.cpp
build correctly the curve keys in  test_curve_proxying.cpp
back to proxy in test_curve_proxying.cpp
Shortened ZMQ_IPC_ACCEPT_FILTER_[UGP]ID to ZMQ_IPC_FILTER_[UGP]ID.
Merge pull request #780 from hashstat/master

Shortened ZMQ_IPC_ACCEPT_FILTER_[UGP]ID to ZMQ_IPC_FILTER_[UGP]ID.
Enable building IPC filtering with cmake.
Move {SO,LOCAL}_PEERCRED checks to C++ context.
Merge branch 'master' of https://github.com/zeromq/libzmq
Merge pull request #781 from hashstat/master

Enable building IPC filtering with cmake and another small autoconf fix.
fix STREAM socket settings and identity size
Add support for extending ZAP request address with IPC peer credentials.

Another take on LIBZMQ-568 to allow filtering IPC connections, this time
using ZAP.  This change is backward compatible.  If the
ZMQ_ZAP_IPC_CREDS option is set, the user, group, and process IDs of the
peer process are appended to the address (separated by colons) of a ZAP
request; otherwise, nothing changes.  See LIBZMQ-568 and zmq_setsockopt
documentation for more information.
Merge pull request #782 from hashstat/master

Add support for extending ZAP request address with IPC peer credentials.
use 127.0.0.1 everywhere for monitoring with wireshark
use zmq_msg for the identity
many changes to test_curve_proxying - backend state machine, NULL worker registration
use mutex implementation if fixed signaler_port!=5905