avcodec: add missing includes

libavcodec/ac3tab.c

@@ -25,6 +25,8 @@
  */
 
 #include "libavutil/channel_layout.h"
+#include "libavutil/mem.h"
+
 #include "avcodec.h"
 #include "ac3tab.h"
 

libavcodec/h261data.c

@@ -26,6 +26,7 @@
 
 #include <stdint.h>
 
+#include "mpegutils.h"
 #include "rl.h"
 #include "h261.h"
 

libavcodec/mjpeg2jpeg_bsf.c

@@ -25,6 +25,10 @@
  */
 
 #include <string.h>
+
+#include "libavutil/error.h"
+#include "libavutil/mem.h"
+
 #include "avcodec.h"
 #include "mjpeg.h"