bethsoftvideo: return meaningful error codes.
bfi: return meaningful error codes.
4xm: eliminate a pointless indirection
bink: return meaningful error codes.
4xm: operate with pointers to AVFrames instead of whole structs.

This is more correct and avoids breaking extended_data.
bink: operate with pointers to AVFrames instead of whole structs.

This is more correct and avoids breaking extended_data.
8bps: return meaningful error codes.
bmp: return meaningful error codes.
aasc: return meaningful error codes.
bmv: return meaningful error codes.
anm: return meaningful error codes
c93: return meaningful error codes.
ansi: return a meaningful error code
yop: use a meaningful error code.
asvdec: return meaningful error codes.
zmbv: return more meaningful error codes.
4xm: return meaningful error codes
aura: return meaningful error codes.
xxan: return meaningful error codes.
4xm: simplify code with FFSWAP