Adds sets of process (Linux only), user, and group IDs for filtering
connections from peer processes over IPC transport.  If all of the
filter sets are empty, every connection is accepted.  Otherwise,
credentials for a connecting process are checked against the filter sets
and the connection is only accepted if a match is found.

This commit is part of LIBZMQ-568 and only adds the filter sets and
implements the filter in the IPC accept method.  The interface for
adding IDs to filter sets are included in a separate commit.

IPC accept filtering is supported only on Linux and OS X.

Code cleanup

changing zmq_proxy_steerable to not use null terminated strings

Fix issue #763

make win32 signaler support ephemeral ports

Fix windows build for type of service.

Add ability to set Differential Services Code Point socket option

Move linger test to issue repo.

See https://github.com/zeromq/issues/pull/7Signed-off-by: Shannen Saez <shannenlaptop@gmail.com>

Moved version macros to top for better visibility

Fixed test_many_sockets

* failed on systems where process could not allocate 1024 sockets by default
* include path for platform.hpp was wrong; fixed it

Fixed typo in documentation about zmq_proxy_steerable()

Added links to RFCs for socket patterns

remove all asserts during critical section for win32 make_fdpair codepath

handle bind error in make_fdpair() win32 codepath

the size of the critical section is reduced by only entering the critical
section right before the bind().

Revert "Make FD_SETSIZE = ZMQ_MAX_SOCKETS_DFLT + 1 so there is room for ...

Removing C++11 code.

This reverts commit 0b92831b.

Update signaler make_fdpair to set file descriptors to -1 when too many ...

Update signaler make_fdpair to set file descriptors to -1 when too many files are open using socketpair.

Fix socket creation above sistem limits for all 'other' OS not covered b...

Fix socket creation above sistem limits for all 'other' OS not covered by eventfd, windows or vms; enhanced test to create sockets up to a bigger limit to really test hitting the OS limit