Generate new generation of agents if (to be) parent generation is old enough.
Usage
PROCREATE(speakerID, hearerID)
Arguments
speakerID
Pointer to first parent
hearerID
Pointer to second parent
Value
Set of new agents
Details
New generation is mix of vocabularies of parents (if world$crossover is T), with emptied usage histories. Agents procreate after number of utterances specified by world$procreationAge. Meanings of words that have not been used by their parents are modified slightly.