I might change this convention again in the future, particularly once
someone wants to fund C89 conformance, but let's stay consistent for
now.
Part of P0264, funded by [Anonymous] and Blue Bolt.
motion_t is also used for certain animations in MAINE.EXE, so not all
instances refer to entities in playfield space. Explicitly specifying
the latter now allows us to gain…
Part of P0149, funded by Blue Bolt, Ember2528, and -Tom-.