Add some kind of DRCS support.

[johnoneil]

DRCS are characters sent within the .ts stream and decoded at runtime. Custom font characters. I doubt this could be supported in .ass files but if the DRCS are common enough (i.e. usually the same two or three characters) i could swap them out for known unicode. The only DRCS i'm familiar with currently are and characters.

Going to add support to parse the DRCS infor and dump it to files and do what I can later.

[johnoneil]

Initial parsing of DRCS is in place but need to hook it up file generation.