re PR c++/88110 (ICE (segfault) with -std=C++2a in cxx_eval_constant_expression when trying to evaluate nonoverridden "virtual ... = 0" function of a base class)

	PR c++/88110
	* constexpr.c (cxx_eval_constant_expression) <case OBJ_TYPE_REF>: Punt
	if get_base_address of ADDR_EXPR operand is not a DECL_P.

	* g++.dg/cpp2a/constexpr-virtual13.C: New test.

From-SVN: r266329