mutter/deps/glib

These are files striped from glib 2.30.2 to build a standalone cogl. A few
changes were done on those imported files:

- the needed functions in gconvert.[ch] have been stubbed (don't want any of the
  charset conversions in error messages in standalone mode,
- gmain.c has been stipped to only have the one used function
  (g_get_current_time()),
- gtestutils.c has also being stripped down to what cogl uses to reduce what it
  pulls in,
- gmessage.c has seen the charset conversions and invalid unicode caracters
  escaping stripped.
- charset conversion in error messages has been removed in gstrfuncs.c
- g_string_append_uri_escaped() has been removed from gstrinc.c
- remove g_get_codeset() from gutils.c