Implement name hiding for macro definitions within modules, such that

Implement name hiding for macro definitions within modules, such that
only the macro definitions from visible (sub)modules will actually be
visible. This provides the same behavior for macros that r145640
provided for declarations.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145683 91177308-0d34-0410-b5e6-96231b3b80d8