[analyzer] Improve localizability checks for iOS / OS X.
Various improvements to the localization checker:
- Adjusted copy to be consistent with diagnostic text in other Apple API checkers.
- Added in ~150 UIKit / AppKit methods that require localized strings in UnlocalizedStringsChecker.
- UnlocalizedStringChecker now checks for UI methods up the class hierarchy and UI methods that conform for a certain Objective-C protocol.
- Added in alpha version of PluralMisuseChecker and some regression tests. False positives are still not ideal.
A patch by Kulpreet Chilana!
Differential Revision: http://reviews.llvm.org/D12417