Reimplementation of NFA to DFA, and Thompson NFA to Glushkov NFA conversions

[katef]

Here I've rewritten these FSM conversions mostly for sake of performance, but also for simplicity. The approach here is focused on trying to do operations in bulk, rather than by doing a sequence of things for each item in turn. This itself gives about a 3x increase over the previous code, but more importantly it sets the scene for future optimisations, in particular for operating on sets of items in parallel.

The Glushkov construction in particular now operates in-situ, rather than by constructing a new FSM.

The diff here is super confusing; github shows this as a modification to the existing determinise.c. Of course that's nonsense, this is a rewrite from scratch (and in fact I did it in separate files before removing the previous implementations). If you're reading this, I suggest looking at determinise.c and glushkov.c just in isolation.

This builds on a lot of previous work; in particular for introducing numeric state indicies (so we can make assumptions about states created in one FSM being equivalent to states in another), and by undertaking epsilon closures in advance.