* decl2.c (add_using_namespace): Iterate over namespaces used
	indirectly.
	* decl.c (lookup_name_real): Accept namespace aliases as locals.
	(cat_namespace_levels): Ignore aliases.
	(duplicate_decls): Ignore duplicate aliases.
	* decl2.c (do_namespace_alias): Process block level namespace
	aliases. Store alias with pushdecl. Remove odr errors.
	* parse.y (namespace_alias): New non-terminal.
	(extdef): Use it.

From-SVN: r21201