range-op: Handle op?.undefined_p () in op[12]_range of comparisons [PR108647]

As mentioned in the PR, we ICE because lhs is singleton [0, 0]
or [1, 1] but op2 (or in other cases op1) is undefined and op?.*_bound ()
ICEs on those because there are no pairs for UNDEFINED.

The following patch makes us set r to varying or return false in those
cases.

2023-02-03  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/108647
	* range-op.cc (operator_equal::op1_range,
	operator_not_equal::op1_range): Don't test op2 bound
	equality if op2.undefined_p (), instead set_varying.
	(operator_lt::op1_range, operator_le::op1_range,
	operator_gt::op1_range, operator_ge::op1_range): Return false if
	op2.undefined_p ().
	(operator_lt::op2_range, operator_le::op2_range,
	operator_gt::op2_range, operator_ge::op2_range): Return false if
	op1.undefined_p ().

	* g++.dg/torture/pr108647.C: New test.