Add support for drtic (dtc) subtitles format

[wesskywalker]

Feature request: add support for drtic subtitles (.dtc extension).

Sample subtitles:

• a.cry.in.the.dark.(1988).eng.1cd.(93610).dtc
• miami.vice.brothers.keeper.(1984).eng.1cd.(4362446).dtc
• psycho.(1960).spa.1cd.(32930).dtc
• grave.of.the.fireflies.(1988).ger.1cd.(111533).dtc
• the.life.of.david.gale.(2003).jpn.2cd.(151590).dtc
• aladdin.(1992).bos.1cd.(4030548).dtc
• the.matrix.(1999).fre.1cd.(114844).dtc

Further information can be found here:

• http://czdream.wz.cz/index_en.html
• http://czdream.wz.cz/about.html
• Latest Version of Subtitle player enigma2
• Advanced Subtitle Downloader
• Drtic - English Tutorial by Pingu v1.2

[bjakja]

It looks like MicroDVD. I can make it load as MicroDVD and treat it as this format and it will work with VSfilter. But for libass it will need to solve issue #348 . When I reveal what's in the header saving as dtc should also be possible.