patch applied (ghc): Check that AT instance is in a class

[chak at cse.unsw.edu.au]

Wed Sep 20 11:38:35 PDT 2006  Manuel M T Chakravarty <chak at cse.unsw.edu.au>
  * Check that AT instance is in a class
  Mon Sep 18 19:16:40 EDT 2006  Manuel M T Chakravarty <chak at cse.unsw.edu.au>
    * Check that AT instance is in a class
    Sat Aug 26 21:49:56 EDT 2006  Manuel M T Chakravarty <chak at cse.unsw.edu.au>
      * Check that AT instance is in a class

    M ./compiler/typecheck/TcInstDcls.lhs -5 +28
    M ./compiler/typecheck/TcTyClsDecls.lhs -3 +5
    M ./compiler/types/TyCon.lhs -8 +25