Replace finite_operands_p with maybe_isnan.

Replace finite_operands_p with maybe_isnan.

The finite_operands_p function was incorrectly named, as it only
returned TRUE when !NAN.  This was leftover from the initial
implementation of frange.  Using the maybe_isnan() nomenclature is
more consistent and easier to understand.

gcc/ChangeLog:

	* range-op-float.cc (finite_operand_p): Remove.
	(finite_operands_p): Rename to...
	(maybe_isnan): ...this.
	(frelop_early_resolve): Use maybe_isnan instead of finite_operands_p.
	(foperator_equal::fold_range): Same.
	(foperator_equal::op1_range): Same.
	(foperator_not_equal::fold_range): Same.
	(foperator_lt::fold_range): Same.
	(foperator_le::fold_range): Same.
	(foperator_gt::fold_range): Same.
	(foperator_ge::fold_range): Same.