Fix make checkheaders by adding missing #include.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@10948 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/huffman.h

@@ -24,6 +24,7 @@
 #define FFMPEG_HUFFMAN_H
 
 #include "avcodec.h"
+#include "bitstream.h"
 
 typedef struct {
     int16_t  sym;