Added instance variable/initializers/getter/setters for new keyword externally initialized to GlobalVariable. No *TRUE* functionality change.

I am going to add in the actual test cases with the actual functionality
changes in a later patch because I want to include some test cases.

To be clear when I say no *TRUE* functionality change I mean that this
patch (like it says in the title) only contains getters/setters and sets
up a default initial value of the instance variable to false so that
this patch does not affect any other uses of Global Variable.h.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174295 91177308-0d34-0410-b5e6-96231b3b80d8