* In our older codebase before the input code was refactored, Exhumed's turning was broken and was only applying the base factor of 12, significantly slower than the other games.
* Upon doing some testing in PCExhumed, I noticed their turning was faster as when the counter meets its target, the turn value is shifted left by 2, effectively making it 48: b90417ed8e/source/exhumed/src/player.cpp (L336-L337)
* Removed this CVAR because of this.
* Reworked turning code so that pressing left+right together cancel each other out and that pressing both doesn't call `updateTurnHeldAmt(scaleAdjust)` twice.
* Redid turn averages factoring in Exhumed's speeds, rounded off values and stored in an enum for clarity.
* 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.
* Added in fca846272e to deal with signed adjustments but its just not needed.
* Made better use of `binangle`/`fixedhoriz` class getters and setters than before as well.
* Based on SW's implementation purely for its commentary, but includes a fix from Duke's.
* Allow disabling Duke's slopetilting via `cl_slopetilting` like SW.
* Preserves the original return to center feel more accurately as original algorithm can't directly translate to pitch. If we ever get rid of Build's horizon throughout the games, this can go on the chopping block then as a necessity.
