move ff_log2_run to bitstream.c and reuse in ffv1.c

Originally committed as revision 13989 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/bitstream.c

@@ -30,6 +30,13 @@
 #include "avcodec.h"
 #include "bitstream.h"
 
+const uint8_t ff_log2_run[32]={
+ 0, 0, 0, 0, 1, 1, 1, 1,
+ 2, 2, 2, 2, 3, 3, 3, 3,
+ 4, 4, 5, 5, 6, 6, 7, 7,
+ 8, 9,10,11,12,13,14,15
+};
+
 /**
  * Same as av_mallocz_static(), but does a realloc.
  *