patch applied (ghc-6.8/ghc): Better error message for unsolvable equalities

[Ian Lynagh]

Mon Sep  3 00:45:28 PDT 2007  Manuel M T Chakravarty <chak at cse.unsw.edu.au>
  * Better error message for unsolvable equalities

    M ./compiler/typecheck/TcTyFuns.lhs -4 +5