WME Subtitles

I've ported Mnemonic's subtitle code from WME1 and tweaked it to go with our style and conventions.

This seems to work well enough with both autodetected and 'regular' subtitle files from my demo game (mov_test from my repo wme_testsuite)

It would feel a bit awkward to me since it's surrounded by C-style strings - in fact, C-style everything.  In this case I would leave it as it is.
Also if I am not mistaken I would still have to use a c-style string to substr tokenStart to and /then/ use that to init my Common::String just to do comparisons with that, so... well, it can be done, but I kind of think it's prettier like this.