Fixed all datum[index] accesses, they are considered undocumented
behavior and fail from 515.1641.
Flipped the OpenDream pragma for the above to emit an error instead of a
warning.
Tweaked gravity check proc to be more inline with TG's version.
Added signals for gravity check, that allows atoms to perform
anti-gravity.
Fixed roller beds thinking they have no gravity and thus not emitting
the rolling sound.
Fixes#19045
Fluffy