patch applied (ghc): Fix generalisation during type inference (again); fixes Trac #1564

[Simon Peyton Jones]

Wed Aug  1 00:26:12 PDT 2007  simonpj at microsoft.com
  * Fix generalisation during type inference (again); fixes Trac #1564
  
  Figuring out which type variables to generalise when inferring the type
  of a let-bound function is always trickier than I think!  This patch
  fixes a bug (related, inevitably, to functional depenencies) found by
  iampure, Trac #1564.  I'll add a test shortly.
  

    M ./compiler/typecheck/TcSimplify.lhs -26 +38