PR lto/66180
	* ipa-devirt.c (type_with_linkage): Check that TYPE_STUB_DECL
	is set; check for assembler name at LTO time.
	(type_in_anonymous_namespace): Remove hacks, check that all
	anonymous types are called "<anon>"
	(odr_type_p): Simplify; add check for "<anon>"
	(odr_subtypes_equivalent): Add odr_type_p check.
	* tree.c (need_assembler_name_p): Even anonymous namespace needs
	assembler name.
	* mangle.c (mangle_decl): Mangle anonymous namespace types as
	"<anon>".
	* g++.dg/lto/pr66180_0.C: New testcase.
	* g++.dg/lto/pr66180_1.C: New testcase.

From-SVN: r223633