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.

test/testaudiocapture.c

@@ -24,7 +24,7 @@ static SDL_AudioDeviceID devid_in = 0;
 static SDL_AudioDeviceID devid_out = 0;
 
 static void
-loop()
+loop(void)
 {
     SDL_bool please_quit = SDL_FALSE;
     SDL_Event e;