PR14606: Debug Info for namespace aliases/DW_TAG_imported_module

This resolves the last of the PR14606 failures in the GDB 7.5 test
suite by implementing an optional name field for
DW_TAG_imported_modules/DIImportedEntities and using that to implement
C++ namespace aliases (eg: "namespace X = Y;").

llvm-svn: 182328
6 files changed