re PR c++/57979 (G++ accepts constant expression defined using floating point non-constexpr glvalue)

	PR c++/57979
	* init.c (decl_really_constant_value): Rename from
	integral_constant_value.
	(scalar_constant_value): Similar but limited to scalar results.
	(decl_constant_value_safe): Remove.
	(constant_value_1): Respect return_aggregate_cst_ok_p.
	* typeck.c (decay_conversion): Use scalar_constant_value.
	* call.c (convert_like_real): Likewise.
	* cvt.c (ocp_convert): No need to check CLASS_TYPE_P.
	* typeck.c (decay_conversion): Or ARRAY_TYPE.
	* constexpr.c (struct constexpr_ctx): Add strict field.
	(cxx_eval_constant_expression) [VAR_DECL]: Use it to select between
	decl_constant_value and decl_really_constant_value.
	(cxx_eval_outermost_constant_expr): Add strict parm.
	(maybe_constant_init): Not strict.
	(potential_constant_expression_1): Add strict parm.
	Shorten most internal calls with RECUR macro.
	* cp-tree.h, pt.c, semantics.c: Adjust.

From-SVN: r217814