re PR c++/87398 (g++ ICE on valid code: tree check: expected record_type or union_type or qual_union_type, have array_type in cxx_eval_constant_expression, at cp/constexpr.c:4820)

	PR c++/87398
	* constexpr.c (cxx_eval_constant_expression) <case OBJ_TYPE_REF>: Only
	look through COMPONENT_REFs with DECL_FIELD_IS_BASE FIELD_DECLs.

	* g++.dg/other/pr87398.C: New test.
	* g++.dg/cpp2a/constexpr-virtual10.C: New test.
	* g++.dg/cpp2a/constexpr-virtual11.C: New test.

From-SVN: r264580