porting: Port for FreeBSD rebased from Mike Ma's efforts

- Provides a working Gluster Management Daemon, CLI
- Provides a working GlusterFS server, GlusterNFS server
- Provides a working GlusterFS client
- execinfo port from FreeBSD is moved into ./contrib/libexecinfo
  for ease of portability on NetBSD. (FreeBSD 10 and OSX provide
  execinfo natively)
- More portability cleanups for Darwin, FreeBSD and NetBSD
- Provides a new rc script for FreeBSD

Change-Id: I8dff336f97479ca5a7f9b8c6b730051c0f8ac46f
BUG: 1111774
Original-Author: Mike Ma <mikemandarine@gmail.com>
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/8141
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>