Updated variable name for mouse coordinates in mouse wheel events

src/events/SDL_mouse.c

@@ -868,8 +868,8 @@ SDL_SendMouseWheel(SDL_Window * window, SDL_MouseID mouseID, float x, float y, S
         event.wheel.preciseX = x;
         event.wheel.preciseY = y;
         event.wheel.direction = (Uint32)direction;
-        event.wheel.mouse_x = mouse->x;
-        event.wheel.mouse_y = mouse->y;
+        event.wheel.mouseX = mouse->x;
+        event.wheel.mouseY = mouse->y;
         posted = (SDL_PushEvent(&event) > 0);
     }
     return posted;