patch applied (ghc): TcUnify.subFunTys must take type families into account

[chak at cse.unsw.edu.au]

Wed Oct 17 04:43:26 PDT 2007  Manuel M T Chakravarty <chak at cse.unsw.edu.au>
  * TcUnify.subFunTys must take type families into account
  * A bug reported by Andrew Appleyard revealed that subFunTys did take
    neither type families nor equalities into account.  In a fairly obscure
    case there was also a coercion ignored.

    M ./compiler/hsSyn/HsUtils.lhs -1 +5
    M ./compiler/typecheck/TcUnify.lhs -15 +41