Core/Movement: allow to manually set up SWIM flag on init splines

Author: ccrs

src/server/game/Movement/Spline/MoveSplineFlag.h

@@ -101,6 +101,7 @@ namespace Movement
         void EnableFacingTarget() { raw() = (raw() & ~Mask_Final_Facing) | Final_Target; }
         void EnableTransportEnter() { raw() = (raw() & ~TransportExit) | TransportEnter; }
         void EnableTransportExit() { raw() = (raw() & ~TransportEnter) | TransportExit; }
+        void EnableSwim() { raw() = raw() | CanSwim; }
 
         uint8 animTier;
         bool done                : 1;

src/server/game/Movement/Spline/MoveSplineInit.h

@@ -144,6 +144,8 @@ namespace Movement
          */
         void SetVelocity(float velocity);
 
+        void SetSwim();
+
         PointsArray& Path() { return args.path; }
 
         /* Disables transport coordinate transformations for cases where raw offsets are available
@@ -164,6 +166,7 @@ namespace Movement
     inline void MoveSplineInit::SetTransportEnter() { args.flags.EnableTransportEnter(); }
     inline void MoveSplineInit::SetTransportExit() { args.flags.EnableTransportExit(); }
     inline void MoveSplineInit::SetOrientationFixed(bool enable) { args.flags.orientationFixed = enable; }
+    inline void MoveSplineInit::SetSwim() { args.flags.EnableSwim(); }
 
     inline void MoveSplineInit::SetParabolic(float amplitude, float time_shift)
     {