frange: drop endpoints to min/max representable numbers for -ffinite-math-only.

frange: drop endpoints to min/max representable numbers for -ffinite-math-only.

Similarly to how we drop NANs to UNDEFINED when -ffinite-math-only, I
think we can drop the numbers outside of the min/max representable
numbers to the representable number.

This means the endpoings to VR_VARYING for -ffinite-math-only can now
be the min/max representable, instead of -INF and +INF.

Saturating in the setter means that the upcoming implementation for
binary operators no longer have to worry about doing the right
thing for -ffinite-math-only.  If the range goes outside the limits,
it'll get chopped down.

Tested on x86-64 Linux.

gcc/ChangeLog:

	* range-op-float.cc (build_le): Use vrp_val_*.
	(build_lt): Same.
	(build_ge): Same.
	(build_gt): Same.
	* value-range.cc (frange::set): Chop ranges outside of the
	representable numbers for -ffinite-math-only.
	(frange::normalize_kind): Use vrp_val*.
	(frange::verify_range): Same.
	(frange::set_nonnegative): Same.
	(range_tests_floats): Remove tests that depend on -INF and +INF.
	* value-range.h (real_max_representable): Add prototype.
	(real_min_representable): Same.
	(vrp_val_max): Set max representable number for
	-ffinite-math-only.
	(vrp_val_min): Same but for min.
	(frange::set_varying): Use vrp_val*.