Inactive rules due to referencing undeclared sprites

[anadrome]

After noticing a typo that made a rule inactive in 687827d, I wondered if there were any others, so wrote a quick Perl script to check. I found two more, but I'm not 100% sure what the fix is for these two, since unlike that case, these aren't obvious typos.

In chipschallenge.txt, the sprite keyused isn't defined, in rule:

keyused avatar > killSprite

In lemmings.txt, the sprite boulder isn't defined, in rule:

boulder wall > stepBack

[diegopliebana]

Thanks! This is fixed (the solution was to simply remove those interactions, as they were ignored).