Otherwise doxygen complains about ambiguous filenames when files exist
under the same name in different subdirectories.

Originally committed as revision 16912 to svn://svn.ffmpeg.org/ffmpeg/trunk

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

Originally committed as revision 13567 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 12319 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 10765 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 9573 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 9572 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 9344 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 8402 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 8401 to svn://svn.ffmpeg.org/ffmpeg/trunk