Fix build and thread runtime compat with older GLib

Fix build and thread runtime compat with older GLib

CentOS 6 ships with glib 2.28.8 which do not support
g_ptr_array_new_full (make-taps/make-dissectors) and need to link with
wsutil for glib-compat.

g_thread_new was only introduced with GLib 2.32 (not 2.31), so adjust
the check accordingly. Abort in case thread creation fails (as
documented). Properly initialize threads or it will abort on runtime
(this also requires linking epan with gthreads in CMake, autotools
already includes it with GLIB_LIBS).

Change-Id: Ie81d6df7b3b26aaa4eb25e23719a220755e2c13c
Reviewed-on: https://code.wireshark.org/review/24978
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Reviewed-by: João Valverde <j@v6e.pt>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>