Language detection fails if DTS is not first track

[LukasKnuth]

If the DTS track is not the first track in the MKV-file (and therefore, -f or -t are specified), the extracted language for the new AC3-track is wrong (it will always be the one of the first audio-track in the file).

The problem is on line 456, where grep -m 1 is used to only get the first occurrence.

An idea for a fix would be to use get all matches and use the DTSTRACK-variable to choose the desired one.

[LukasKnuth]

It seems the output of mkvinfo has changed in version mkvinfo v6.0.0 ('Coming Up For Air'). The Audio-Track output part is now:

+ A track
|  + Track number: 2 (track ID for mkvmerge & mkvextract: 1)
|  + Track UID: 3838534841
|  + Track type: audio             <<< HERE. There is no information of what type the stream is.
|  + Default flag: 0
|  + Codec ID: A_DTS               <<< THE information is now here.
|  + Default duration: 10.667ms (93.750 frames/fields per second for a video track)
|  + Language: ger
|  + Audio track
|   + Sampling frequency: 48000
|   + Channels: 6

Which doesn't match the old pattern anymore: grep -m 1 "audio (A_DTS)". This causes $DTSTRACK to be always empty and every DTS-track get's "eng" as it's language. Working on it...

[1951FDG]

Opened pull request (#87)