Add range intersect with 2 wide-ints.

Add range intersect with 2 wide-ints.

Add a more efficent intersect using a lower/upper bound single pair of
wide_ints.

	* gimple-range-cache.cc (non_null_ref::adjust_range): Call new
	intersect routine.
	* gimple-range-fold.cc (adjust_pointer_diff_expr): Ditto.
	(adjust_imagpart_expr): Ditto.
	* value-range.cc (irange::irange_intersect): Call new routine if
	RHS is a single pair.
	(irange::intersect): New wide_int version.
	* value-range.h (class irange): New prototype.