add screenpressor SCPR binary decoder

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36460 b3059339-0415-0410-9bf9-f77b7e298cf2
mpeg123: Support in-stream format changes.

Also fixes bugzilla #2149.

Patch by Thomas Orgis [thomas-forum orgis org].

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36461 b3059339-0415-0410-9bf9-f77b7e298cf2