Bug 1397 - Allow localizing the command line help

Bug 1397 - Allow localizing the command line help

Clutter has a set of command line options that are added to every
application by means of clutter_init() or by obtaining the Clutter
GOptionGroup and using g_option_context_parse(). Thus, every Clutter
application will automatically have an --help command line switch
showing the list of options and their description.

At the moment, Clutter does not enable localization of the help,
thus making it less than useful on non-English locales.

This patch enables the machinery to create a localization file and
load it when initializing Clutter, by means of the GLib macros and
locale.h API we already use.

Signed-off-by: Emmanuele Bassi <ebassi@linux.intel.com>