Dust on landing, gas on letting go, and a lander that stays let go

One particle system, three uses now: a lander coming apart, dust kicked
up by a landing, and gas out of a docking port on release. Where they
start, how fast they go, what colour they are and how long they last are
arguments; everything else is shared.

Dust goes sideways and UP off the lander's feet, because that is where
kicked dust goes and there is ground in the way of the rest of it. Gas
goes evenly in every direction, because nothing is in the way of a
docking port. Neither happens on docking - a dock is a catch and not a
touchdown, and there is nothing under it to kick.

---- Ticked from the frame loop, not run in place ----

The explosion can afford to stop the world; there is nothing left to fly.
The undocking puff cannot, because it goes off on the frame a thruster is
pressed, and freezing a quarter of a second exactly then is felt as the
controls sticking. So a burst advances one frame at a time from the main
loop, and the two that can afford to wait just pump that same tick until
the air is clear.

---- And letting go did not let go ----

Which the puff is what found. A docked lander sits EXACTLY one tile under
the station, so releasing upwards moved it towards the station and it
docked again on the very next frame: took the fuel again, said so again,
and waited to be told the message had been read - which reads as the
controls locking up the instant they are used.

It has to get clear now before it can take hold again, and the two
distances have to differ: docking wants one tile, re-arming wants two.
A single distance re-armed on the frame it let go, because a tile is
exactly where it was sitting.

Three checks, each seen to fail on its own break. The last of them
measures HOW FAR the lander has got and not merely that it moved: a
sixteen frame pause on release still leaves it climbing, four rows short
of a free run, so "it moved" would pass for a stall that has been slept
through.

Tests/expected/cosmosSprite.out

@@ -22,7 +22,7 @@ Mode.sbx                48
 Flip.sbx                173
 Sprite.sbx              442
 Depth.sbx               672
-Lander.sbx              7913
+Lander.sbx              8243
 Pad.sbx                 264
 Crash.sbx               632
 vars.script             50