allow XSUB/XPUB to send/recv messages unrelated to sub/unsub

zmq::xpub_t::xread_activated() – change to process messages without 0
or 1 prefix, but without affecting subscriptions

zmq::xsub_t::xsend() – change to send rather than discard messages
without 0 or 1 prefix, but without affecting subscriptions

Update documentation

Fix minor problem with cmake bulid

Make CMake build usable for other systems

Fix link errors when using -m32 with MinGW

The CPack NSIS installer was in a state where it would always give a
useless error. I think it was using stuff intended for running cpack
separately from cmake.

Fix warnings with ICC.

Make doc building option dependent on asciidoc being installed
Fix MSVC build requiring cygwin.
Don't use try_run to get the version

fix for LIBZMQ-84: Address already in use (signaler.cpp)

eliminate dead code moved into zmq_utils.cpp

TIME_WAIT state.

win32: fix Event handle leak

Pull upstream OpenPGM 5.2.122 for multi-platform minor fixes.

returns -1 with EAGAIN when mandatory is set and pipe is full

return EHOSTUNREACH at full only when mandatory is set