The XSETTINGS key that matches the :fontconfig-timestamp property on ClutterSettings.
Simple mapping between XSETTINGS key and ClutterSettings property. http://bugzilla.clutter-project.org/show_bug.cgi?id=2583
Use the XSETTINGS machinery to get notification from foreign environments about settings that might interest Clutter itself - namely: the default font name, the font DPI, and the Xft font options that can be mapped on cairo_font_options_t.
