Change the types of typed brackets and splices.
The essence of this change is that a TExp a now wraps a TH.Exp instead of a TH.ExpQ. This means: * A typed bracket [||...||] now has type Q (TExp tau), where tau is the type of the expression in the bracket. * A typed splice $(...) must contain a value of type Q (TExp tau), and has type tau. Previously, typed brackets had type TExp tau, and typed splices had to contain a value of type TExp tau.