Document 'ic' variable. See "[PATCH] RDT/Realmedia patches #2" thread in ML.

Originally committed as revision 15916 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/rdt.c

@@ -36,7 +36,7 @@
 #include <libavcodec/bitstream.h>
 
 struct RDTDemuxContext {
-    AVFormatContext *ic;
+    AVFormatContext *ic; /**< the containing (RTSP) demux context */
     AVStream *st;
     void *dynamic_protocol_context;
     DynamicPayloadPacketHandlerProc parse_packet;