- the return value of url_open_dyn_*buf() is 0 on success, so using
   if (!(res = url_open_dyn_*buf())) return res; is not going to work
- url_open_dyn_packet_buf actually writes the max_packet_size before
   each piece of data. Feeding this to the ASF demuxer will never work.
   Therefore, use url_open_dyn_buf() instead.



git-svn-id: file:///var/local/repositories/ffmpeg/trunk@21853 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b