A big hole where the evaluator used to be...

[Neil Jerram]

Exciting times!  Much kudos to Andy, who has just merged a big and
interesting change, the effect of which is essentially to stop using the
old C-coded evaluator.

(Actually it's not quite true that there's only a hole left.  We still
need a basic C evaluator for bootstrapping, but it's much smaller and
simpler than what was there before.)

FWIW, building and make check all look good to me.  There are some
noticeable benchmark changes - some slower and some faster - which I'll
look more into.

Regards,
        Neil