Don't access RMContext directly in rdt.c. Rather, use the return value of

Don't access RMContext directly in rdt.c. Rather, use the return value of
ff_rm_parse_packet() to indicate whether more audio packets are available
in the demuxer from the last RM frame, and save that in the RDT parsing
context. See patch/discussion in "[PATCH] rdt.c: don't access RMContext"
on ML.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@16110 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b