avcodec/rpza: Perform pointer advance and checks before using the pointers

Fixes out of array accesses
Fixes Ticket2850

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 3819db745da2ac7fb3faacb116788c32f4753f34)

Conflicts:

	libavcodec/rpza.c
(cherry picked from commit edba432b8b01d68c22e70a508f47553359f59fb5)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
matroska_read_seek: Fix used streams for subtitle index compensation

Might fix Ticket1907 (I have no testcase so i cant test)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 4758e32a6c48044f77102a49110c79b4f338f648)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/dsputil: fix signedness in sizeof() comparissions

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 454a11a1c9c686c78aa97954306fb63453299760)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/ffv1enc: update buffer check for 16bps

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 3728603f1854b5c79d1a64dd3b41b80640ef1e7f)

Conflicts:

	libavcodec/ffv1enc.c
(cherry picked from commit c900c6e5c26cd86cf34f9c8d4347cedbd01f3935)