avutil: add AVERROR_UNKNOWN

Useful to return instead of -1 when the cause of the error is unknown,
typically from an external library.

doc/APIchanges

@@ -12,6 +12,9 @@ libavutil:   2011-04-18
 
 API changes, most recent first:
 
+2012-xx-xx - xxxxxxx - lavu 51.24.0 - error.h
+  Add AVERROR_UNKNOWN
+
 2012-xx-xx - xxxxxxx - lavc 54.x.x
   Add duration field to AVCodecParserContext
 

libavutil/avutil.h

@@ -153,8 +153,8 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR 51
-#define LIBAVUTIL_VERSION_MINOR 23
-#define LIBAVUTIL_VERSION_MICRO  1
+#define LIBAVUTIL_VERSION_MINOR 24
+#define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
                                                LIBAVUTIL_VERSION_MINOR, \

libavutil/error.c

@@ -39,6 +39,7 @@ int av_strerror(int errnum, char *errbuf, size_t errbuf_size)
     case AVERROR_PROTOCOL_NOT_FOUND:errstr = "Protocol not found"                           ; break;
     case AVERROR_STREAM_NOT_FOUND:  errstr = "Stream not found"                             ; break;
     case AVERROR_BUG:               errstr = "Bug detected, please report the issue"        ; break;
+    case AVERROR_UNKNOWN:           errstr = "Unknown error occurred"                       ; break;
     }
 
     if (errstr) {

libavutil/error.h

@@ -58,6 +58,7 @@
 #define AVERROR_PROTOCOL_NOT_FOUND (-MKTAG(0xF8,'P','R','O')) ///< Protocol not found
 #define AVERROR_STREAM_NOT_FOUND   (-MKTAG(0xF8,'S','T','R')) ///< Stream not found
 #define AVERROR_BUG                (-MKTAG( 'B','U','G',' ')) ///< Bug detected, please report the issue
+#define AVERROR_UNKNOWN            (-MKTAG( 'U','N','K','N')) ///< Unknown error, typically from an external library
 
 /**
  * Put a description of the AVERROR code errnum in errbuf.