loadso: library handles are now SDL_SharedObject* instead of void*.

Improved the SDL_loadso.h documentation a little, too.

Fixes #11009.

src/render/direct3d11/SDL_render_d3d11.c

@@ -153,8 +153,8 @@ typedef struct
 // Private renderer data
 typedef struct
 {
-    void *hDXGIMod;
-    void *hD3D11Mod;
+    SDL_SharedObject *hDXGIMod;
+    SDL_SharedObject *hD3D11Mod;
     IDXGIFactory2 *dxgiFactory;
     IDXGIAdapter *dxgiAdapter;
     IDXGIDebug *dxgiDebug;