Rather sporadic cleanup

Hi Daniel,

Been quite a while since I last pushed any changes, but I'm afraid I have made a few scattered modifications in a pretty unorganised fashion; hope it's not too much bother to look through it.
[4603b9c0](https://github.com/leftaroundabout/HaTeX/commit/4603b9c07ff59a849983753ec6839c48e1e6dbce) is a plain bug fix, I'd made an incorrect assumption about `comm0` in the implementation of `autoBraces`.