[analyzer] Don't issue alarm in ObjCSuperCallChecker for the super class itself.

The ObjCSuperCallChecker issues alarms for various Objective-C APIs that require
a subclass to call to its superclass's version of a method when overriding it.
So, for example, it raises an alarm when the -viewDidLoad method in a subclass
of UIViewController does not call [super viewDidLoad].

This patch fixes a false alarm where the analyzer erroneously required the
implementation of the superclass itself (e.g., UIViewController) to call
super.

rdar://problem/18416944

Differential Revision: http://reviews.llvm.org/D11842

llvm-svn: 244386