Remove 'copy_names' parameter from add_using_directive

I noticed that add_using_directive's 'copy_names' parameter is only
used by a single caller.  This patch removes the parameter and changes
that caller to copy the names itself.  I chose to use intern here
since I suspect the names may well be repeated in a given objfile.

Approved-By: John Baldwin <jhb@FreeBSD.org>

gdb/cp-namespace.c

@@ -100,8 +100,9 @@ cp_scan_for_anonymous_namespaces (struct buildsym_compunit *compunit,
 		 to 0, this way it is always considered valid.  */
 	      std::vector<const char *> excludes;
 	      add_using_directive (compunit->get_local_using_directives (),
-				   dest, src, NULL, NULL, excludes, 0,
-				   1, &objfile->objfile_obstack);
+				   objfile->intern (dest), objfile->intern (src),
+				   nullptr, nullptr, excludes, 0,
+				   &objfile->objfile_obstack);
 	    }
 	  /* The "+ 2" is for the "::".  */
 	  previous_component = next_component + 2;