Add correct_movement, call from CL_CreateMove

src/features/movement.c

@@ -1,10 +1,12 @@
 
 #include <stdio.h>
+#include <math.h>
 
 #include "features.h"
 #include "../include/sdk.h"
 #include "../include/globals.h"
 #include "../include/cvars.h"
+#include "../include/util.h"
 
 static void autostrafe_legit(usercmd_t* cmd) {
     /* Get mouse delta */
@@ -41,3 +43,24 @@ void bhop(usercmd_t* cmd) {
         }
     }
 }
+
+/*
+ * Unfortunately I don't know shit about math, so this is pasted from:
+ *   https://github.com/deboogerxyz/ahc/blob/0492646e28dd7234a8cd431d37b152dc18a21b04/ahc.c#L377
+ */
+void correct_movement(usercmd_t* cmd, vec3_t old_angles) {
+    float old_y = old_angles[1] + (old_angles[1] < 0 ? 360 : 0);
+    float new_y = cmd->viewangles[1] + (cmd->viewangles[1] < 0 ? 360 : 0);
+    float delta = (new_y < old_y) ? fabsf(new_y - old_y)
+                                  : 360 - fabsf(new_y - old_y);
+
+    delta = 360 - delta;
+
+    float forward = cmd->forwardmove;
+    float side    = cmd->sidemove;
+
+    cmd->forwardmove =
+      cos(DEG2RAD(delta)) * forward + cos(DEG2RAD(delta + 90)) * side;
+    cmd->sidemove =
+      sin(DEG2RAD(delta)) * forward + sin(DEG2RAD(delta + 90)) * side;
+}