ext/ogg/: Fix the case where the muxer would mark pages as delta frames when they are not (vorbis only ogg).

Original commit message from CVS:
* ext/ogg/gstoggdemux.c: (gst_ogg_pad_push):
* ext/ogg/gstoggmux.c: (gst_ogg_mux_next_buffer),
(gst_ogg_mux_send_headers), (gst_ogg_mux_loop):
Fix the case where the muxer would mark pages as delta
frames when they are not (vorbis only ogg).