Every thruster that catches pops, not only the first

A pilot already burning upwards who then adds a sideways thruster has lit
an engine, and that is what an engine lighting sounds like. So what is
watched is now the SET of thrusters rather than whether any of them is
lit: the bits on now that were not on before, which is an exclusive or
and an and and no comparison at all.

The rumble still asks the old question, because it is the right question
for it - struck when the first lights and not again until every one has
gone out. Restriking it when a second joins would start its attack over,
which is a stutter rather than an engine, so it keeps a flag of its own.

Pitches are as tuned by ear: 36 for the pop, 60 for the rumble.

Checked by two flights of the same length, one thruster held throughout
against one that gains a second in the middle. The rumble is identical in
both, so the whole of the difference is the extra pop: peak 11,452 against
15,540, and the recordings diverge at 3.19 seconds, which is the frame the
second thruster lights.

Tests/expected/cosmosMonitor.out

@@ -108,7 +108,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              9168
+Lander.sbx              9220
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50