On some versions of gcc, these weren't always getting inlined due to hitting
the inline cap limit in some files. This is generally bad, as most of these
functions are smaller inlined than not.
(cherry picked from commit eb3755a5aa65da685d81399cfae4bd35e4a178b6)
This reduces the number of false dependencies on header files and
speeds up compilation.
Originally committed as revision 22407 to svn://svn.ffmpeg.org/ffmpeg/trunk
