https://gcc.gnu.org/ml/gcc-patches/2019-10/msg01707.html
	* cp-tree.c (CPTI_STD_IDENTIFIER): Delete.
	(std_identifier): Delete.
	(DECL_NAME_SPACE_STD_P): Compare against std_node.
	* decl.c (initialize_predefined_identifiers): 'std' is not needed.
	(cxx_init_decl_processing): Adjust creation of ::std.  Use
	{push,pop}_nested_namespace.
	(cxx_builtin_function): Use {push,pop}_nested_namespace.
	* except.c (init_exception_processing): Likewise.
	* rtti.c (init_rtti_processing): Likewise.

From-SVN: r277365