Fix interpolation when curling up or scaling while flipped

Fixes player interpolation when curling up or otherwise changing height while in reverse gravity (fixes #983 (closed)).
Fixes scaling interpolation while flipped.
Fixes the NiGHTS Drone interpolating its "first-tic flip"-Z adjustment (which might not have been interpolated in the first place due to it being on its first tic?).

-

TL;DR: Fixed some interpolation artefacts.