Outlaw etc. death polishing

[sprunk]

There are tiny differences when "delayed death" units (Outlaw, Limpet) die compared to others:

• wreck does not inherit velocity. Could do it manually or wait for this engine feature.
• fresh wreck does not smoke. Not solvable via Lua atm, requires either this or this.
• targeted orders (e.g. repair) aren't dropped immediately and you can see them point underground for a bit. This works for tacnukes (who use a different script than outlaw etc) so just copy that over.
• homing projectiles get confused, see Underground unit hiding leads to homing issues #2214. It has its own ticket so I'm just listing it here for completeness.