Contains the following (related to problems found while investigting...

Contains the following (related to problems found while investigting <rdar://problem/6497631> Message lookup is sometimes different than gcc's).

- Implement instance/class overloading in ObjCContainerDecl (removing a FIXME). This involved hacking NamedDecl::declarationReplaces(), which took awhile to figure out (didn't realize replace was the default).
- Changed Sema::ActOnInstanceMessage() to remove redundant warnings when dealing with protocols. For now, I've omitted the "protocol" term in the diagnostic. It simplifies the code flow and wan't always 100% accurate (e.g. "Foo<Prot>" looks in the class interface, not just the protocol).
- Changed several test cases to jive with the above changes.

llvm-svn: 65292