patch applied (ghc): Fixes to data type families

[Simon Peyton Jones]

Wed May  2 03:28:11 PDT 2007  simonpj at microsoft.com
  * Fixes to data type families
  
  - Fix two distinct bugs, one in MkId.mkDataConIds, one in DataCon.mkDataCon
  - Add more comments
  - Add a little assertion checking in TyCon
  
  Type-family tests now work.
  

    M ./compiler/basicTypes/DataCon.lhs -6 +12
    M ./compiler/basicTypes/MkId.lhs -22 +26
    M ./compiler/types/TyCon.lhs -7 +56