avcodec/vorbisdec: try to workaround libvorbisenc bug

Fixes Ticket3590

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 0a266cb55af9794fc5cff695d35cae4111e4334f)
sws: dont use the optimized 410->420 unscaled conversion when height%4

Fixes Ticket3594
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 421b21ca8a02a346ba03cea3bb2ecc33f791fc30)