Add test using fair or length bounding without preemption bounding

[barrucadu]

All the systematic tests use preemption bounding (PB). The backtracking for fair bounding (FB) is disabled when doing PB, as the set of backtracking points identified by PB is sufficient. But this means we're not testing the case where we have FB but no PB.

Similarly, we're not testing the case where we only length bounding (LB).

I think this would be best tested by adding some examples with spinlocks, and running them (a) with FB and LB but no PB, and (b) with just LB.

W and TEST introduced in #197 makes it possible to test arbitrary Ways.