mace: Make sure that the channel count is set to a valid value

Also return a proper error code.

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>
(cherry picked from commit e1f3847f860a1094a46be4c5f10db8df616c3135)
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Conflicts:
	libavcodec/mace.c
matroskadec: Verify realaudio codec parameters

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>
(cherry picked from commit 569d18aa9dc989c37bb4d4b968026fe5afa6fff9)
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
(cherry picked from commit 9f7a8b8f8f6ad024410232d926b774261ef2ef36)
rv34: Check the return value from ff_rv34_decode_init

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>
(cherry picked from commit 711c970168297683860422e95d6b7e37ee3c8367)
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
(cherry picked from commit 20c8f176293e7520c6205b664e25ecf8a711253e)