AlienWeakTable sends #copyGrownBy: to both of its internal arrays, but
it looks like neither Squeak nor Pharo implement it in the collection
hierarchy. Pharo has #grownBy:, but Squeak doesn't. So in Alien-Core-
kdt.59, I implemented SequenceableCollection>>copyGrownBy: by copying
in the Pharo implementation of #grownBy:.
This should solve some nastiness that could happen when the table hit
its initial maximum (1024 objects).