visibility is enabled) or leave and re-enter it, restore the macro and module
visibility state from last time we were in that submodule.

This allows mutually-#including header files to stand a chance at being
modularized with local visibility enabled.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237871 91177308-0d34-0410-b5e6-96231b3b80d8