move evaluator after the loop; remove unroller
move evaluator after the loop; remove unroller

the evaluator is no longer part of the iterative loop
that attempts to do inlining and type-checking by
repeatedly applying substitutions and checks; it needs
to be done after this loop, and is all-or-nothing
(it can't be restarted if it fails)

The unroller is also removed from the loop, since its
functionality is handled by the evaluator (and it's
no longer entirely correct -- the evaluator is better)

BBN-Q/pyqgl2,BBN-Q/pyqgl2