Add AVERROR_EXIT.

This is different from AVERROR(EINTR) because calls that fail with EINTR
should usually be restarted.
Signed-off-by: Nicolas George <nicolas.george@normalesup.org>
Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>

libavutil/error.c

@@ -37,6 +37,7 @@ int av_strerror(int errnum, char *errbuf, size_t errbuf_size)
     case AVERROR_FILTER_NOT_FOUND:  errstr = "Filter not found"; break;
     case AVERROR_BSF_NOT_FOUND:     errstr = "Bitstream filter not found"; break;
     case AVERROR_STREAM_NOT_FOUND:  errstr = "Stream not found"; break;
+    case AVERROR_EXIT:              errstr = "Immediate exit requested"; break;
     }
 
     if (errstr) {

libavutil/error.h

@@ -66,6 +66,8 @@
 #define AVERROR_BSF_NOT_FOUND      (-MKTAG(0xF8,'B','S','F')) ///< Bitstream filter not found
 #define AVERROR_STREAM_NOT_FOUND   (-MKTAG(0xF8,'S','T','R')) ///< Stream not found
 
+#define AVERROR_EXIT (-MKTAG('E','X','I','T')) ///< Immediate exit was requested; the called function should not be restarted
+
 /**
  * Put a description of the AVERROR code errnum in errbuf.
  * In case of failure the global variable errno is set to indicate the