- add support for deblocking_filter_idc==2 which means no deblocking accross slice.
- correct MMCO with multiple slices.

5 more streams from H264 conformance suite are now correctly decoded.

patch by (Loic <lll+ffmpeg >< m4x dot org>)

Originally committed as revision 3786 to svn://svn.ffmpeg.org/ffmpeg/trunk