Add GLua syntax highlighting to the Error output

It would be really cool if we could syntax highlight the error output.

Since we've monkey-patched `MsgC` to write everything in ANSI, it's doable.

I think the best place to start would be finding the source for some existing syntax highlighter (`gcompute`? `luapad`? some css highlighter?) written in lua and hack it to output ANSI color codes instead.

It'll be tricky, but it would be a really cool addition.