Re-enable rotation for thrown projectiles

Related to #8925.

Rotation towards the falling direction was disabled for thrown projectiles because of undesirable roll angle changes caused by makeRotate picking the shortest angle, which can have an arbitrary roll component. This isn't particularly noticeable for bolts/arrows, but it's pretty noticeable for thrown projectiles. Regardless, both should try to avoid unnecessary roll.

Caveat: this (rather overengineered) solution also nullifies the roll if the shooting direction is straight up because it becomes impossible to reconstruct it based purely off the shooting direction. A better solution might be to store the initial Z angle, change the X angle based on the direction and calculate the quaternion based on them, but that requires changing how magic projectiles work too (and the saved game format). This was also an issue with the original implementation. I think this is a decent reference (visually) for a more precise implementation otherwise, though.

Doesn't make the Improved Thrown Weapon Projectiles situation any worse.

To test, throw some knives and stars.