Log Message:
libmp4v2: fix build more properly.

if 0 likely out of bounds write, we only have one scratch channel,
don't write to a second if asked to do stereo (thanks, GCC 4.5.3!)

convert lowercase min, max to uppercase - libstdc++6 doesn't approve
of it. mostly using sed, because there's too many occurences.

if we're not returning anything, use a void return type.

fix likely issue with signed char - 0251 may be truncated, but the
equivalent \xa9 won't be.

don't store a return value if we're not going to check it.

correct misleading indentation.

Remove -fpermissive too, as it caused jperkin issues. I could build
without removing -Werror, but I'll keep it since it's full of warnings.

XXX do we want a security advisory for this, if it can be triggered?