added functions gst_gconf_get_default_{audio,video}_sink -- this is so the defaults library (gstgconf) can be used by...

Original commit message from CVS:
added functions gst_gconf_get_default_{audio,video}_sink -- this is so the
defaults library (gstgconf) can be used by applications with uninstalled gstreamer
(ie, no gconf keys). More specifically, these functions enable the player to
work uninstalled, which is a good thing (tm).