* Remove unused `getincanglef()`.
* Remove unused `getincangleq16()`.
* In `PlayerHorizon` struct, clamp value when setting target in `__settarget()`, not each public `settarget()` overload.
* Rename `PlayerAngle` method `applylook()` to `applyinput()`.
* Rename `PlayerHorizon` method `sethorizon()` to `applyinput()`.
* In `PlayerHorizon::applylook()`, slightly clean return to centre code so it doesn't do math if already at 0.
* In `PlayerAngle::applylook()`, slightly clean rotscrnang/look_ang code so it doesn't do math if already at 0 and reposition where mouse input is applied so that if input is applied, the player never enters a spin.
* In `Duke3d::player_struct::apply_seasick()`, use `buildfang()` method instead of scaling float to BAM within function.
* Initial implementation from d32dcd5f8e was not working properly and already had some workarounds for when the player was underwater, etc.
* Re-read implementation in GDX and rebased off of it.
* Fixes#303.
