This is something I've been thinking of doing for awhile. The
automatic leaving can be frustrating if you were trying to collect
the money dropped by the enemy and you're suddenly forced out of
the mission. This prevents that by simply waiting to do the exit
sequence until no worthwhile collectables are left in the area.
Ellesh and Mars are excluded since this won't really work in those
areas. Also excluded by Classic and Nightmare difficulties.
This was done with "replace all" actions, but I have checked and
the only collatoral damage has been to capitalize some instances
of "objective" in comments.
The fourth is simply a duplicate of ship_collision for bullets. A
bit redundant, but I figure it's clearer of a definition. Besides,
this opens up the door to possibly making bullets a different struct
type in the future, if that turns out to be desirable.