[analyzer] New checker for missing super calls in UIViewController subclasses.

[analyzer] New checker for missing super calls in UIViewController subclasses.

This is a syntactic checker aimed at helping iOS programmers correctly
subclass and override the methods of UIViewController. While this should
eventually be covered by the 'objc_requires_super' attribute, this
checker can be used with the existing iOS SDKs without any header changes.

This new checker is currently named 'alpha.osx.cocoa.MissingSuperCall'.
Patch by Julian Mayer!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@166993 91177308-0d34-0410-b5e6-96231b3b80d8