Hydro 'r' flag.

[only_a_ptr]

I've just validated a bug report from DannyWerewolf on Discord:

• on current stable release (2022.04) and prior, the `hydros` flag `r` (rudder input) also works for land vehicles and, quote: On current release, with "r" is exactly how it should be, and about how fast the trucks have always steered with default sensitivity on controller.
• on current git master branch, when `r` flag is present, the hydro doesn't respond to keyboard at all.

I'm going to investigate what hapenned and later document this "trick" because I like when players get creative with the software and find edge cases. I'm also keen to maintain backwards compatibility.

The reason I'm posting this here: do you have any other useful insights to working with `hydros` (or maybe other active N/B) that isn't documented anywhere?