Fix for instantiate-test (see core). Also remove dead code from jpegenc (which still needs fixing, but that's lower o...

Original commit message from CVS:
2004-01-07  Ronald Bultje  <rbultje@ronald.bitfreak.net>

* ext/audiofile/gstafsink.c: (gst_afsink_init), (gst_afsink_chain),
(gst_afsink_handle_event):
* ext/jpeg/gstjpegenc.c: (gst_jpegenc_init):
* gst/avi/gstavimux.c: (gst_avimux_request_new_pad):
* sys/dxr3/dxr3audiosink.c: (dxr3audiosink_init):
* sys/dxr3/dxr3spusink.c: (dxr3spusink_init):
* sys/dxr3/dxr3videosink.c: (dxr3videosink_init):
Fix for instantiate-test (see core). Also remove dead code from
jpegenc (which still needs fixing, but that's lower on my TODO
list...).
* sys/v4l2/gstv4l2src.c: (gst_v4l2src_getcaps):
Never return NULL as caps.