PR14606: Debug info for using directives/DW_TAG_imported_module

More changes later for using declarations/DW_TAG_imported_declaration.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179837 91177308-0d34-0410-b5e6-96231b3b80d8
Revert "PR14606: Debug info for using directives/DW_TAG_imported_module"

This reverts commit r179837 as it seems to be causing test failures.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179839 91177308-0d34-0410-b5e6-96231b3b80d8