Compile with ghc-7.9.x

The next version of GHC/template-haskell makes `Pred` a synonym for `Type` (to support ConstraintKinds) and makes the integers in the `Name` type lifted. This patch gets th-lift to compile with GHC HEAD, while (hopefully) not sacrificing other compatibility. I've tested on GHC 7.8.3, but not other versions.