Rules and suchlike

[Simon Peyton-Jones]

I've just done a massive commit, which aims to improve
support for rules, primarily.  The commit messages say it all,
and I've done my best to test, but be warned -- the HEAD may
not be very stable for a few days.

urg.  I've just remembered I'm out tomorrow... if it fails you can
always check out today's version again.

Manuel... let me know how it goes.
There are examples of the new inlining and RULE syntax in
PrelBase.  The main "script" is in DriverState (alas).


Simon