ObjCMessageExpr objects that represent messages to class methods now can...

ObjCMessageExpr objects that represent messages to class methods now can contain the ObjCInterfaceDecl* of the target class if it was available when the ObjCMessageExpr object was constructed.  The original interfaces of the class has been preserved (requiring no functionality changes from clients), but now a "getClasSInfo" method returns both the ObjCInterfaceDecl* and IdentifierInfo* of the target class.

llvm-svn: 52676