patch applied (ghc-6.8/ghc): Improve error messages from type-checking data constructors

[Ian Lynagh]

Fri Feb 22 10:25:14 PST 2008  simonpj at microsoft.com
  * Improve error messages from type-checking data constructors
  
  This addresses Trac #2112
  

    M ./compiler/typecheck/TcHsType.lhs -9 +5
    M ./compiler/typecheck/TcRnMonad.lhs -1 +1
    M ./compiler/typecheck/TcTyClsDecls.lhs -1 +2