Add SubViewer v1 subtitles demuxer and decoder.

libavcodec/allcodecs.c

@@ -456,6 +456,7 @@ void avcodec_register_all(void)
     REGISTER_ENCDEC (SRT,               srt);
     REGISTER_ENCDEC (SUBRIP,            subrip);
     REGISTER_DECODER(SUBVIEWER,         subviewer);
+    REGISTER_DECODER(SUBVIEWER1,        subviewer1);
     REGISTER_DECODER(TEXT,              text);
     REGISTER_DECODER(VPLAYER,           vplayer);
     REGISTER_DECODER(WEBVTT,            webvtt);