patch applied (ghc): FIX #1688: Givens in checkLoop are not that rigid after all

[chak at cse.unsw.edu.au]

Wed Sep 19 08:07:38 PDT 2007  Manuel M T Chakravarty <chak at cse.unsw.edu.au>
  * FIX #1688: Givens in checkLoop are not that rigid after all
  - This patch re-instates the policy of 6.6.1 to zonk the given constraints
    in the simplifier loop.
  
  MERGE TO STABLE

    M ./compiler/typecheck/TcSimplify.lhs -4 +45