* ipa-devirt.c (type_pair, default_hashset_traits): New types.
	(odr_types_equivalent_p): Use pair hash.
	(odr_subtypes_equivalent_p): Likewise, do structural compare
	on ODR types that may be mismatched.
	(warn_odr): Support warning when only one field is given.
	(odr_types_equivalent_p): Strenghten comparsions made;
	support VOIDtype.
	(add_type_duplicate): Update VISITED hash set.

From-SVN: r215328