Add ARM NEON optimization of common channel interleave cases.

While the code is certainly far from optimal, it is about
3 times faster.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36488 b3059339-0415-0410-9bf9-f77b7e298cf2
ARM NEON optimization for float->int conversion.

Not optimal, but since lrintf is incredibly slow on
ARM it is > 10x faster than the old code.
A fallback solution that (incorrectly) defines lrintf(x)
as (int)(x) might make sense to avoid these kind of issues
for the pure C code, however we would still need to know whether
lrintf is slow or not.
Though maybe the better solution was if all architectures provided
a non-braindead implementation of lrintf.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36489 b3059339-0415-0410-9bf9-f77b7e298cf2
Remove pointless cast.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36490 b3059339-0415-0410-9bf9-f77b7e298cf2
Remove some macros and switch to libavutil equivalents.

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@36491 b3059339-0415-0410-9bf9-f77b7e298cf2