Remove all remaining code that was disabled through the major version bump.

Originally committed as revision 17903 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/mathematics.c

@@ -55,12 +55,6 @@ int64_t av_gcd(int64_t a, int64_t b){
     else  return a;
 }
 
-#if LIBAVUTIL_VERSION_MAJOR < 50
-int64_t ff_gcd(int64_t a, int64_t b){
-    return av_gcd(a, b);
-}
-#endif
-
 int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding rnd){
     int64_t r=0;
     assert(c > 0);