jill/src/main/java/io/github/agentsoz/jill/lang/IntentionStacks.java
Stack255 nextActiveStack() {
    activeStack = (activeStack + 1) % stacks.size();
    return (Stack255) stacks.get(activeStack);
  }
Stack255 nextActiveStack() {
    activeStack = (activeStack + 1) % stacks.size();
    return (Stack255) stacks.get(activeStack);
  }
Makes the next intentions stack active using a round robin scheme.
@return the newly active stack.