Use an specific lock for FontConfig. Hopefully it fixes some crashes

Use an specific lock for FontConfig. Hopefully it fixes some crashes

2006-12-18  Carlos Garcia Campos  <carlosgc@gnome.org>
	* backend/ev-document.[ch]: (ev_document_get_fc_mutex),
	(ev_document_fc_mutex_lock), (ev_document_fc_mutex_unlock):
	* pdf/ev-poppler.cc: (make_thumbnail_for_size):
	* shell/ev-jobs.c: (ev_job_render_run), (ev_job_fonts_run):
	* shell/ev-view.c: (draw_loading_text):
	* shell/ev-window.c: (ev_window_cmd_file_properties):
	Use an specific lock for FontConfig. Hopefully it fixes some crashes
	related to using FontConfig from different threads.