Add fun/fn captures, operator-likes, and some builtins to language def

You can test with this theme:

https://github.com/mreinhardt/tmThemes/blob/master/Clouds%20Midnight%20II.tmTheme

...to see clearly what my language definition changes do.

I'm fairly new to SML so let me know if I got anything majorly wrong or left something out of one of my defs.