evolve: make fold aware of allowunstable Before this patch, the fold command was performing the same way regardless of the value of experimental.evolution. With this patch if the configuration does not allow unstability, fold won't create instability.

evolve: make prune respect allowunsable Before this patch, the prune command was performing the same way regardless of the value of experimental.evolution. With this patch if the configuration does not allow unstability, prune won't create instability.