lavf/mpsub: remove sscanf from probing.

This should make probing faster.
jpeg2000dec: fix memleaks in error cases in jpeg2000_decode_frame()

Reviewed-by: Nicolas BERTRAND <nicoinattendu@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Support decoding of Lagarith frame type FRAME_SOLID_COLOR.

Fixes bug 459.