Huge wad of changes from GHC team

- Rename Compat.* modules to Distribution.Compat.*
- Add {-# OPTIONS -cpp #-} to a few modules
- Distribution.Compat.ReadP: use real ReadP in GHC 6.3+
- new module: Distribution.Extension, contains Extension type
  formerly from Distribution.Misc.
- new module: Distribution.License, contains License type
  formerly from Distribution.Misc.
- remove Distribution.Misc
- new module: Distribution.ParseUtils, containing various parsing utilities
  formerly from Distribution.Package, that are re-used in 
  Distribution.InstalledPackageInfo.
- new module: Distribution.PackageDescription contains everything related
  to PackageDescription, which was formerly in Distribution.Package.
- Distribution.Package now contains only PackageId-related stuff.
- Distribution.InstalledPackageInfo: update for use in GHC, add
  parsing/pretty-printing.
- Compat.H98 is now Distribution.Compat.Error (it contained only stuff
  related to the Error monad, which isn't H98 anyway).
- remove imports of H98 libs (use hierarchical ones instead)
- configure now detects the GHC version (but doesn't do anything with it... yet)