gst/rtp/: Add a jpeg depayloader.

gst/rtp/: Add a jpeg depayloader.

Original commit message from CVS:
* gst/rtp/Makefile.am:
* gst/rtp/gstrtp.c: (plugin_init):
* gst/rtp/gstrtpjpegdepay.c: (gst_rtp_jpeg_depay_base_init),
(gst_rtp_jpeg_depay_class_init), (gst_rtp_jpeg_depay_init),
(gst_rtp_jpeg_depay_finalize), (MakeTables), (MakeQuantHeader),
(MakeHuffmanHeader), (MakeDRIHeader), (MakeHeaders),
(gst_rtp_jpeg_depay_setcaps), (gst_rtp_jpeg_depay_process),
(gst_rtp_jpeg_depay_change_state),
(gst_rtp_jpeg_depay_plugin_init):
* gst/rtp/gstrtpjpegdepay.h:
Add a jpeg depayloader.
* gst/rtp/gstrtpjpegpay.c:
Set the default properties on the payloader to better defaults.