PR fortran/64104

	* expr.c (gfc_check_init_expr): Allow some IEEE functions in
	constant expressions.
	(external_spec_function): Allow some IEEE functions in specification
	expressions.
	* simplify.c (gfc_simplify_ieee_selected_real_kind): Remove.
	(simplify_ieee_selected_real_kind, simplify_ieee_support,
	matches_ieee_function_name, gfc_simplify_ieee_functions): New
	functions.
	* gfortran.h (gfc_simplify_ieee_selected_real_kind): Remove
	prototype.
	(gfc_simplify_ieee_functions): Add prototype.

	* gfortran.dg/ieee/ieee_8.f90: New test.

From-SVN: r226723