Fix race condition in nextStep on high refresh rate displays

[rinevard]

On high refresh rate displays, nextStep() can be called multiple times before STEP++ executes, since nextStep is called every CLOCK frames, while STEP++ is scheduled by setTimeout. This leads to false WIN triggers in the "Complex-Prevent" puzzle.

Example: The first nextStep() is called. Before its scheduled infect and STEP++ execute, the second nextStep() is called. Then the callbacks run in order: first infect, first STEP++, second infect, second STEP++. Since both infect calls target the same peep, the infection count doesn't change between the two STEP++ increments. However, after the first STEP++, state.lastInfected in the "Complex-Prevent" onupdate is updated. When the second STEP++ triggers another onupdate check, lastInfected == countInfected evaluates to true, falsely triggering the win condition.

Before fix:

before.mp4

After fix:

after.mp4