[PATCH 4 of 4 V2] obsolete: allow cycles

[Jun Wu]

Excerpts from Jun Wu's message of 2017-03-21 22:42:11 -0700:
> The key here is the order of operation 2 and 3. If 2 happens after 3, then B
> gets hidden as expected. Currently, this cycle will get both B and C hidden,
> which I don't think is a sane behavior.

Sorry. It should be "Currently, 3 is always treated as happened before 2".
There are no cycles in this simple case.