- Memory and registers are split up into typed atomic cells
- Value type now contains only scalar values
- Instructions are compiled down to WMM "operations", allowing stores
  and loads of composite values to be split up into atomic parts
- Scheduler now executes one operation at a time, rather than one block
  at a time
- New scheduler steps for WMM
- Commands (formerly Thread Actions) such as allocation now executed at
  the global scheduler level. Action IDs no longer needed.
- Threads and stacks changed completely; registers now stored in stack
  frames
- Monads pretty-print properly again!
- Patricia trees replaced with sptrees

Lots of code is still commented out, and tests still don't work, but
the main formalization code compiles.