- Use "for_expression" rather than "allow_unknownanytype"

  to indicate that we're doing stuff for the expression
  parser.

- When for_expression is true, look through @s and find
  the actual class rather than just returning id. 

- Rename BuildObjCObjectType to BuildObjCObjectPointerType
  since it's actually returning an object *pointer* type.

llvm-svn: 220979