tiff: frame multithreading support

Signed-off-by: Paul B Mahol <onemda@gmail.com>
doc/filters: reformat scale filter doc

Signed-off-by: Stefano Sabatini <stefasab@gmail.com>
avcodec/gsmdec: reject unsupported msn audio modes

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>