0) Typo in panic message.
1) prioritization of equalities over family equalities in the worklists.
2) rewriting of inert substitutions and solveds on-the-spot instead of
   kicking them out in the inerts. This required a monadic map over
   substitutions hence the modifications in UniqFM.
3) Just comments and removing stale commented code.

4) Useful SCC for simplifyInfer.

5) Making CoreStats outputable.