ext/vorbis/vorbisenc.*: Fix EOS handling.  Still needs a fix in the ogg muxer to mark the last page as eos somehow.

Original commit message from CVS:
2005-09-15  Thomas Vander Stichele  <thomas at apestaart dot org>

* ext/vorbis/vorbisenc.c: (gst_vorbisenc_init),
(gst_vorbisenc_sink_event), (gst_vorbisenc_chain),
(gst_vorbisenc_output_buffers), (gst_vorbisenc_change_state):
* ext/vorbis/vorbisenc.h:
Fix EOS handling.  Still needs a fix in the ogg muxer to
mark the last page as eos somehow.