ext/gdk_pixbuf/gstgdkpixbuf.c: Add state change function where we set 0/1 as default framerate in case our setcaps fu...

Original commit message from CVS:
* ext/gdk_pixbuf/gstgdkpixbuf.c: (gst_gdk_pixbuf_sink_setcaps),
(gst_gdk_pixbuf_class_init), (gst_gdk_pixbuf_flush),
(gst_gdk_pixbuf_sink_event), (gst_gdk_pixbuf_change_state):
Add state change function where we set 0/1 as default framerate in
case our setcaps function isn't called, like it might not in a
filesrc ! gdkpixbufdec scenario. Fixes assertion triggered by
gdkpixbufdec trying to create caps with a 0/0 framerate.
Also post an error message on the bus if gst_pad_push() fails when
called from our sink event handler (+1 for flow returns for event
functions in 0.11) instead of failing silently.