will clear out the stream. I think that this is really a linux bug in
  the handling of poll, but I did a workaround anyway.
* Improve the statistics output and prevent a buffer overrun when lots
  of clients are connected.
* Process ffm input when it is received and don't always be one ffm
  packet behind.
* Try to avoid going through the poll loop when not required.

Originally committed as revision 514 to svn://svn.ffmpeg.org/ffmpeg/trunk