[jhc] darcs patch: create a better relation representation, ... (and 4 more)

Fri Aug 6 01:26:22 PDT 2010 John Meacham * create a better relation representation, speed up export chasing signifigantly Fri Aug 6 02:03:49 PDT 2010 John Meacham * split type environment into concrete and mutable sets, to avoid retraversing the concrete imported types Fri Aug 6 02:28:15 PDT 2010 John Meacham * further seperate out concrete types to speed up checking Fri Aug 6 04:17:03 PDT 2010 John Meacham * speed up name choosing a little Fri Aug 6 04:28:20 PDT 2010 John Meacham * clean ups