gst/realmedia/: Add RealMedia RTSP extension module. It has rank NONE until it is...

gst/realmedia/: Add RealMedia RTSP extension module. It has rank NONE until it is fully functional.

Original commit message from CVS:
* gst/realmedia/Makefile.am:
* gst/realmedia/rmdemux.c: (plugin_init):
* gst/realmedia/rtspreal.c: (rtsp_ext_real_get_transports),
(rtsp_ext_real_before_send), (rtsp_ext_real_after_send), (hash),
(call_hash), (rtsp_ext_real_calc_response_and_checksum),
(rtsp_ext_real_parse_sdp), (rtsp_ext_real_stream_select),
(_do_init), (gst_rtsp_real_base_init), (gst_rtsp_real_class_init),
(gst_rtsp_real_init), (gst_rtsp_real_finalize),
(gst_rtsp_real_change_state), (gst_rtsp_real_extension_init),
(gst_rtsp_real_plugin_init):
* gst/realmedia/rtspreal.h:
Add RealMedia RTSP extension module. It has rank NONE until it is fully
functional.