Consistently apply this rule: the guard name is obtained from the
filename by stripping the leading "lib", converting '/' and '.' to
'_' and uppercasing the resulting name. Guard names in the root
directory have to be prefixed by "FFMPEG_".
Originally committed as revision 15120 to svn://svn.ffmpeg.org/ffmpeg/trunk
libavutil/common.h for platforms with no inttypes.h.
patch by Steve Lhomme, slhomme divxcorp com
Originally committed as revision 6790 to svn://svn.ffmpeg.org/ffmpeg/trunk
