add missing declaration for av_md5_sum

Originally committed as revision 5583 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/md5.h

@@ -8,6 +8,7 @@ struct AVMD5;
 void av_md5_init(struct AVMD5 *ctx);
 void av_md5_update(struct AVMD5 *ctx, const uint8_t *src, const int len);
 void av_md5_final(struct AVMD5 *ctx, uint8_t *dst);
+void av_md5_sum(uint8_t *dst, const uint8_t *src, const int len);
 
 #endif /* MD5_H */