Add two new APIs for active keyboard layout.

This goes with https://github.com/adobe/brackets/pull/9652.
I think you just want the `LOWORD` to pass to `GetLanguageFromId()` according to http://msdn.microsoft.com/en-us/library/windows/desktop/ms646296(v=vs.85).aspx, the `LOWORD` of the return value from `GetKeyboardLayout()` is the Language ID.