* For RR, `processweapon_r()` was performing angle and horizon changes directly which provided a harsh experience with the default `cl_syncinput 0` mode.
* Added `angAdjust` variable to `player_struct` for use with ticrate angle adjustments.
* Renamed `horizAngleAdjust` to `horizAdjust` so that there is less confusion with the new `angAdjust` variable.
* Removed `horizSkew` variable, can just use `horizAdjust` for this.
* Replaced all calls to `addang()` and `addhoriz()` with the appropriate additions/subtractions to `angAdjust` and `horizAdjust` respectively.
* Removed now unused `addang()` and `addhoriz()` setters from `player_struct`.
* Define new function `resetinputhelpers()` to eliminate code duplication between `processinput_d()` and `processinput_r()` functions.
* Remove `p->q16ang` and `p->q16horiz` direct setting from `FinalizeInput()`.
* Change `applylook()` to accept an `fixed_t adjustment` for changing the player's angle. This can either be `input.q16avel` when `cl_syncinput` is 0, or `sync[snum].q16angvel` when `cl_syncinput` is 1.
* Change `sethorizon()` to accept an `fixed_t adjustment` for changing the player's horizon. This can either be `input.q16horz` when `cl_syncinput` is 0, or `sync[snum].q16horz` when `cl_syncinput` is 1.
* Re-work `sethorizon()` to always adjust `p->q16horiz` using the true pitch code. This closer resembles the EDuke32 implementation as per SVN 7342.
* Re-work returning to center to work off the true pitch code and always ensure that the player returns to center.
* Implement work-around for RR where we need to call `sethorizon()` before the call to `fi.doincrements()` like the original game, but also after the call to `processweapon()` to apply any angle or horizon changes due to weapon recoil, etc. We work around this by calling `sethorizon()` from within `doincrements_r()` only if `cl_syncinput` is 1 and only if `doincrements_r()` is to return 1.
* Current setup was broken and unusable.
* Fixed interpolation issues.
* Only call `GetInput()` at frame-rate when `cl_syncinput` is 0.
* Create `oq16look_ang` and interpolate it for enhanced smoothness.
* Always reset `horizAngleAdjust` and `horizSkew` in `processinput_d()`.
* Don't pre-scale `sb_avel` in `processinput_d()` and `processinput_r()`.
* Promote `p->angvel` from short to fixed_t.
* Don't descale `sync[snum].q16horz` in `processinput_d()` and `processinput_r()`.
* Ensure `false` bool is provided to `sethorizon()` call in `processinput_d()` and `processinput_r()`.
* Reset `p->q16angvel` in `resetplayerstats()`.
