patch applied (ghc): Refactoring of where tcSimplifyTop happens

[Simon Peyton Jones]

Wed Nov 22 05:51:21 PST 2006  simonpj at microsoft.com
  * Refactoring of where tcSimplifyTop happens
  
  We want to do tcSimplifyTop after checkMain, because checkMain can add
  useful type information that eliminates ambiguity.  E.g.
  	main = return undefined
  
  This is the way it used to be in 6.6, and I think I mistakenly moved it
  when doing implication constraints. This patch effectively puts it back
  the way it was.
  
  Cures the cg053 failure.
  

    M ./compiler/typecheck/TcRnDriver.lhs -29 +36