Fix warning for Android NDK compiler: "function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]"

https://stackoverflow.com/questions/42125/warning-error-function-declaration-isnt-a-prototype
In C int foo() and int foo(void) are different functions. int foo() accepts an arbitrary number of arguments, while int foo(void) accepts 0 arguments. In C++ they mean the same thing.

(cherry picked from commit ccade50587)

test/testscale.c

@@ -78,7 +78,7 @@ void Draw(DrawState *s)
     SDL_RenderPresent(s->renderer);
 }
 
-void loop()
+void loop(void)
 {
     int i;
     SDL_Event event;