split and sort.

Heresy now has a very robust string split function that takes an
optional list of delimiters.

There is also a sort function. It may be slightly less robust, but only
because I haven't defined macros for string < or >.

I also fixed some comments to more accurately describe what left$ and
right$ do, and I'm considering changing what they do to be something
more useful. It really seems like they should take the left or right
half from a pivot index, rather than taking X from left or right. The
latter seems less useful.