Tweak Sema::ActOnInstanceMessage() to look for a class method when dealing with quali...

Tweak Sema::ActOnInstanceMessage() to look for a class method when dealing with qualified id's. This change is motivated by our desire to not support the "Class<foo>" idiom. Note that the change makes perfect sense (since all ObjC classes are also id/instances).

This allow us to document a simple migration path...change "Class <foo>" to "id <foo>".

This effects:
- <rdar://problem/6761939> TASK: File source change radars for "qualified Class" errors
- <rdar://problem/6761864> Protocol qualified Class is unsupported

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@68517 91177308-0d34-0410-b5e6-96231b3b80d8