Add subtitle support. It recognises the subtitle channels, but does not seem to include them in the converted file.

Example:
Stream #0.0[0x1011]: Video: h264, yuv420p, 1920x1080, 23.98 tbr, 90k tbn, 23.98 tbc
Stream #0.1[0x1100](eng): Audio: dca, 48000 Hz, 5:1, 1536 kb/s
Stream #0.2[0x1200](nld): Subtitle: 0x0090
Stream #0.3[0x1201](nld): Subtitle: 0x0090
Output #0, vob, to 'U:\movie.mpg':
Stream #0.0: Video: mpeg2video, yuv420p, 1920x1080, q=2-31, 12000 kb/s, 90k tbn, 23.98 tbc
Stream #0.1(eng): Audio: ac3, 44100 Hz, 5:1, 128 kb/s
Stream mapping:
Stream #0.0 -> #0.0
Stream #0.1 -> #0.1

Stream 0.2 and 0.3 are forgotten...