Add SDL_main.h includes to tests

.. including cmake/test/*.c, whatever that does

(this is needed now because SDL.h doesn't include SDL_main.h anymore)

test/loopwavequeue.c

@@ -19,6 +19,7 @@
 #endif
 
 #include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
 
 #if HAVE_SIGNAL_H
 #include <signal.h>