Fixed Minus badnik gravflip bugs

[Turret 49]

The rocks that Minus badniks create when they jump in and out of the ground don't despawn if they're gravflipped.
The Minus' animation doesn't account for being gravflipped either, causing it to dig in and out of the ground bottom-first.

 

[MeowingCuteKittyCats]

The minus is probably expected to only be placed on the floor and not the ceiling. The rocks are probably coded to despawn upon hitting a floor, but since they're flipped and on the ceiling, they aren't touching the actual floor.

 

[glaber]

Wow, that's worse than Minus 2.0

 

[sphere]

Fix Minus & debris' reverse gravity behavior (!1764) · Merge requests · STJr / SRB2 · GitLab

Fixes https://mb.srb2.org/threads/minus-badnik-gravflip-bugs.34569/, and debris not despawning in reverse gravity in general.

git.do.srb2.org