SDL2: Use precise mouse wheel values

[Menduist]

https://wiki.libsdl.org/SDL2/SDL_MouseWheelEvent

    Sint32 x;           /**< The amount scrolled horizontally, positive to the right and negative to the left */
    Sint32 y;           /**< The amount scrolled vertically, positive away from the user and negative toward the user */
[...]
    float preciseX;     /**< The amount scrolled horizontally, positive to the right and negative to the left, with float precision (added in 2.0.18) */
    float preciseY;     /**< The amount scrolled vertically, positive away from the user and negative toward the user, with float precision (added in 2.0.18) */

SDL 2.0.18 was released in 2021

[raysan5]

@Menduist thanks for the update