When building types from declarators, instead of building two types (one for

the DeclaratorInfo, one for semantic analysis), just build a single type whose
canonical type will reflect the semantic analysis (assuming the type is
well-formed, of course).

To make that work, make a few changes to the type system:
* allow the nominal pointee type of a reference type to be a (possibly sugared)
  reference type.  Also, preserve the original spelling of the reference type.
  Both of these can be ignored on canonical reference types.
* Remove ObjCProtocolListType and preserve the associated source information on
  the various ObjC TypeLocs.  Preserve the spelling of protocol lists except in
  the canonical form.
* Preserve some level of source type structure on parameter types, but
  canonicalize on the canonical function type.  This is still a WIP.

Drops code size, makes strides towards accurate source location representation,
slight (~1.7%) progression on Cocoa.h because of complexity drop.

llvm-svn: 84907