lavc: add a wrapper for AVCodecContext.get_buffer().

It will be useful in the upcoming transition to refcounted AVFrames.

libavcodec/apedec.c

@@ -26,6 +26,7 @@
 #include "avcodec.h"
 #include "dsputil.h"
 #include "bytestream.h"
+#include "internal.h"
 
 /**
  * @file
@@ -909,7 +910,7 @@ static int ape_decode_frame(AVCodecContext *avctx, void *data,
 
     /* get output buffer */
     s->frame.nb_samples = blockstodecode;
-    if ((ret = avctx->get_buffer(avctx, &s->frame)) < 0) {
+    if ((ret = ff_get_buffer(avctx, &s->frame)) < 0) {
         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
         return ret;
     }