re PR c++/88446 (__builtin_is_constant_evaluated rejects some converted constant...

re PR c++/88446 (__builtin_is_constant_evaluated rejects some converted constant expressions.)

	PR c++/88446
	* cp-tree.h (maybe_constant_value): Add manifestly_const_eval
	argument.
	* constexpr.c (struct constexpr_call): Rename pretend_const_required
	member to manifestly_const_eval.
	(struct constexpr_ctx): Likewise.
	(constexpr_call_hasher::equal): Adjust users.
	(cxx_eval_builtin_function_call): Likewise.  Formatting fix.
	(cxx_eval_call_expression): Adjust users.
	(cxx_eval_outermost_constant_expr, maybe_constant_init_1,
	maybe_constant_init): Rename pretend_const_required argument to
	manifestly_const_eval, adjust function comments.
	(maybe_constant_value): Add manifestly_const_eval argument.  If true,
	don't cache and call cxx_eval_outermost_constant_expr with true as
	manifestly_const_eval.
	* decl.c (compute_array_index_type_loc): Call maybe_constant_value
	with true as manifestly_const_eval.

	* g++.dg/cpp2a/is-constant-evaluated3.C: New test.

From-SVN: r267047