Return true if a useless computation was removed.

The case where the consequent and alternative are equal did not
set the bit correctly.

While this might lead to user-visible changes, such as more memory
being collected, it certainly is mainly observable when a live
visualization shows the control flow which is still alive (before
this change there were spurious disconnected <computation> nodes)
Cleanup references of an inlined computation

Previously there were some leftovers in the flow graph, but since
being disconnected not a big issue. It is observable in the
visualization, though. This change is most likely not observable
to an user.