patch applied (ghc): Further compileToCore improvements

[Kirsten Chevalier]

Thu Jun 28 18:48:31 PDT 2007  Tim Chevalier <chevalier at alum.wellesley.edu>
  * Further compileToCore improvements
  
  Per suggestions from Simon M:
  
  * Changed GHC.checkModule so that it doesn't call depanal.
  * Changed GHC.checkModule to optionally return Core bindings
  as a component of the CheckedModule that it returns (and 
  resulting changes to HscMain.hscFileCheck).
  * As a result, simplified GHC.compileToCore and changed it
  to load the given file so that the caller doesn't have to.

    M ./compiler/ghci/InteractiveUI.hs -1 +1
    M ./compiler/main/GHC.hs -44 +39
    M ./compiler/main/HscMain.lhs -6 +14