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
move it from sdp.c into utils.c. Also add new header internal.h specifically
for lavf-specific internal API. See discussion in "Realmedia patch" thread
on mailinglist.
Originally committed as revision 15002 to svn://svn.ffmpeg.org/ffmpeg/trunk
