patch applied (ghc): More refactoring in TcSimplify

[Simon Peyton Jones]

Wed Jun 20 02:36:46 PDT 2007  simonpj at microsoft.com
  * More refactoring in TcSimplify
  
  This re-jig tides up the top-level simplification, and combines in one
  well-commented function, approximateImplications, the rather ad-hoc
  way of simplifying implication constraints during type inference.
  
  Error messages get a bit better too.
  

    M ./compiler/typecheck/TcSimplify.lhs -85 +105