Add VPlayer subtitles demuxer and decoder.

Note that the linebreaks text codec option (but not the feature) has
been removed; its main goal was to allow demuxers to configure the text
decoder (and not meant to be used by users), but the AVOption are not a
viable solution. This is solved differently in this commit.

libavcodec/allcodecs.c

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