re PR c++/53756 ([C++1y] ICE: in gen_type_die_with_usage, at dwarf2out.c:18774 with -g and operator auto ())

	PR c++/53756
gcc/
	* dwarf2out.c (auto_die): New static.
	(gen_type_die_with_usage): Handle C++1y 'auto'.
	(gen_subprogram_die): If in-class DIE had 'auto', emit type again
	on definition.
gcc/cp/
	* mangle.c (write_unqualified_name): Handle operator auto.

From-SVN: r207197