Globally rename the header inclusion guard names.
Consistently apply this rule: the guard name is obtained from thefilename by stripping the leading "lib", converting '/' and '.' to'_' and uppercasing the resulting name. Guard names in the rootdirectory have to be prefixed by "FFMPEG_"....
improve CRC API - don't export any global var - provide either generated or hardcoded tables
Originally committed as revision 11409 to svn://svn.ffmpeg.org/ffmpeg/trunk