smaccmpilot: Compiler version comment update.
smaccmpilot: Slight refactoring of Stabilize module.

- Define "constrain" as an Ivory procedure rather than a Haskell
  function that returns an Ivory expr.  I don't think it can be
  polymorphic this way, which costs a bit of power, but it makes
  the generated code nicer.
- Add some comments explaining the PI algorithm.
- Fix DSL source location in "ghci.sh".