re PR c++/77830 (internal compiler error: in output_constructor_regular_field, at varasm.c:4968, when using constexpr (with testcase))

	PR c++/77830
	* constexpr.c (cxx_eval_array_reference): Perform out of bounds
	verification even if lval is true, just allow one past the last
	element in that case.
	(cxx_eval_store_expression): Detect stores to out of bound
	ARRAY_REF.

	* g++.dg/cpp1y/pr77830.C: New test.
	* g++.dg/cpp0x/pr65398.C: Adjust expected diagnostics.

From-SVN: r243873