PROTON-348: Platform neutral helper functions for examples and tests.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1503531 13f79535-47bb-0310-9956-ffa450edef68
PROTON-364: Install C examples.

Added a install variable, EXAMPLES_INSTALL_DIR.

Installs the send.c, recv.c, CMakeLists.txt files from the
examples/messenger/c directory. Also installs the getopt.c and getopt.h
files, related LICENSE, and the misc_defs.h and misc_funcs.inc files.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1506653 13f79535-47bb-0310-9956-ffa450edef68