patch applied (ghc): Add a warning flag for when the Prelude is implicitly imported (trac #1317)

[Simon Peyton Jones]

Fri May 11 01:45:25 PDT 2007  Isaac Dupree <id at isaac.cedarswampstudios.org>
  * Add a warning flag for when the Prelude is implicitly imported (trac #1317)
  GHC already determines all the implicit (Prelude) imports,
  so we just need to check whether there are any of those,
  for each module being compiled.

    M ./compiler/main/DynFlags.hs +2
    M ./compiler/rename/RnNames.lhs +7
    M ./docs/users_guide/flags.xml -1 +8
    M ./docs/users_guide/using.xml +26