Fix error return for clock_gettime.

Problem: build break in OSX, VS2010, VS2012

thread safety bug - lock when sending

Revert "Bzimmerman cmake"

problem: client and server sockets are not thread safe

Problem: VS projects missing client/server.

Bzimmerman cmake

added version to builds
other cleanup

Problem: Cross compile for iOS isn't working for auxiliary tools

acinclude.m4: make kernel-specific flags cacheable

Specifically when cross-compiling, one can be willing to force these
variable values using the environment of a config.cache file. This
commit makes this possible.

The affected variables are:

* libzmq_cv_sock_cloexec
* libzmq_cv_so_keepalive
* libzmq_cv_tcp_keepcnt
* libzmq_cv_tcp_keepidle
* libzmq_cv_tcp_keepintvl
* libzmq_cv_tcp_keepalive
Signed-off-by: Lionel Orry <lionel.orry@gmail.com>

Add missing EOL at EOF.

problem: jenkins build failed

problem: client socket is missing