Summary:
There were overly complex and different ways of identifying C++/objC languages. Simplify and unify them.
How I came up with naming - there are two languages C and C++. You can apply "Objective-" extention to both of them.
We usually need to differentiate C and C++ (different AST) and whether it's extended (checks specific to ObjC)
Reviewed By: dulmarod
Differential Revision: D3804457
fbshipit-source-id: 685e40a