Equivalent to nullptr

[Stanislav Blinov via Digitalmars-d-learn]

In the meantime, you can get around the issue by redeclaring the 
function with another name and loading it manually just after 
calling DerelictSDL2.load():

>import derelict.sdl2.sdl;
>
>__gshared SDL_bool function (const(SDL_Point)*, int, 
>const(SDL_Rect)*, SDL_Rect*) SDL_EnclosePoints_;
>
>void main()
>{
>    DerelictSDL2.load();
>    DerelictSDL2.bindFunc(cast(void**)&SDL_EnclosePoints_, 
> "SDL_EnclosePoints");
>    // ...
>}

Now you'd need to call SDL_EnclosePoints_ instead of 
SDL_EnclosePoints.