Add -Wincomplete-module, which detects when a header is included from a module but isn't itself part of a module.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182263 91177308-0d34-0410-b5e6-96231b3b80d8
Fix broken test

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182264 91177308-0d34-0410-b5e6-96231b3b80d8