AVI demuxer: return AVERROR_EOF upon detection of end of file.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@17456 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavformat/avidec.c

@@ -870,7 +870,7 @@ resync:
         }
     }
 
-    return -1;
+    return AVERROR_EOF;
 }
 
 /* XXX: We make the implicit supposition that the positions are sorted