Patch by flybird2k at gmail

Originally committed as revision 24307 to svn://svn.ffmpeg.org/ffmpeg/trunk

Also put compute_antialias_integer() under !CONFIG_FLOAT and change
forward declarations to declare only the relevant one of these.

Fixes warnings about unused functions and pointer type mismatches.

Originally committed as revision 23950 to svn://svn.ffmpeg.org/ffmpeg/trunk

Should allow for future SIMD optimizations.

Originally committed as revision 23912 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 23743 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 23095 to svn://svn.ffmpeg.org/ffmpeg/trunk