error: define AVERROR_BUFFER_TOO_SMALL.

Some API require a buffer and return a specific error
if it is too small. This error code helps to map codes.

libavutil/error.c

@@ -31,6 +31,7 @@ struct error_entry error_entries[] = {
     { ERROR_TAG(BSF_NOT_FOUND),      "Bitstream filter not found"                     },
     { ERROR_TAG(BUG),                "Internal bug, should not have happened"         },
     { ERROR_TAG(BUG2),               "Internal bug, should not have happened"         },
+    { ERROR_TAG(BUFFER_TOO_SMALL),   "Buffer too small"                               },
     { ERROR_TAG(DECODER_NOT_FOUND),  "Decoder not found"                              },
     { ERROR_TAG(DEMUXER_NOT_FOUND),  "Demuxer not found"                              },
     { ERROR_TAG(ENCODER_NOT_FOUND),  "Encoder not found"                              },

libavutil/error.h

@@ -48,6 +48,7 @@
 
 #define AVERROR_BSF_NOT_FOUND      FFERRTAG(0xF8,'B','S','F') ///< Bitstream filter not found
 #define AVERROR_BUG                FFERRTAG( 'B','U','G','!') ///< Internal bug, also see AVERROR_BUG2
+#define AVERROR_BUFFER_TOO_SMALL   FFERRTAG( 'B','U','F','S') ///< Buffer too small
 #define AVERROR_DECODER_NOT_FOUND  FFERRTAG(0xF8,'D','E','C') ///< Decoder not found
 #define AVERROR_DEMUXER_NOT_FOUND  FFERRTAG(0xF8,'D','E','M') ///< Demuxer not found
 #define AVERROR_ENCODER_NOT_FOUND  FFERRTAG(0xF8,'E','N','C') ///< Encoder not found