demux, stream: rip out the classic stream cache

The demuxer cache is the only cache now. Might need another change to
combat seeking failures in mp4 etc. The only bad thing is the loss of
cache-speed, which was sort of nice to have.

stream/stream_edl.c

@@ -6,7 +6,6 @@
 static int s_open (struct stream *stream)
 {
     stream->demuxer = "edl";
-    stream->allow_caching = false;
 
     return STREAM_OK;
 }