WIP: bugfix for rare flapping infinite loop (fixed I hope)
WIP: bugfix for rare flapping infinite loop (fixed I hope)

I'll run a set of PULSE tests (Cmd_e of the 'regression' style)
to try to confirm a fix for this pernicious little thing.

Final (?) part of the fix: add myself to SeenFlappers in
react_to_env_A30().

cmeiklejohn/machi,cmeiklejohn/machi,basho/machi,basho/machi,basho/machi