[analyzer] Add checkers for OS X / iOS localizability issues

Add checkers that detect code-level localizability issues for OS X / iOS:
  - A path sensitive checker that warns about uses of non-localized
    NSStrings passed to UI methods expecting localized strings.
  - A syntax checker that warns against not including a comment in
    NSLocalizedString macros.

A patch by Kulpreet Chilana!

(This is the second attempt with the compilation issue on Windows and
the random test failures resolved.)

llvm-svn: 245093