Implement poly-kinded Typeable
This patch makes the Data.Typeable.Typeable class work with arguments of any kind. In particular, this removes the Typeable1..7 class hierarchy, greatly simplyfing the whole Typeable story. Also added is the AutoDeriveTypeable language extension, which will automatically derive Typeable for all types and classes declared in that module. Since there is now no good reason to give handwritten instances of the Typeable class, those are ignored (for backwards compatibility), and a warning is emitted. The old, kind-* Typeable class is now called OldTypeable, and lives in the Data.OldTypeable module. It is deprecated, and should be removed in some future version of GHC.