lavu: Deprecate AVFrame.error[]

These field are difficult to interpret, and are provided by a single
encoder (mpegvideoenc). In general they do not belong to a structure
containing raw data only, so remove them from AVFrame.

Mpegvideoenc now uses a private field in Picture for its internal
computations.

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

libavutil/frame.h

@@ -240,10 +240,13 @@ typedef struct AVFrame {
      */
     void *opaque;
 
+#if FF_API_ERROR_FRAME
     /**
-     * error
+     * @deprecated unused
      */
+    attribute_deprecated
     uint64_t error[AV_NUM_DATA_POINTERS];
+#endif
 
     /**
      * When decoding, this signals how much the picture must be delayed.