x11/wayland: fix screensaver suspension via D-Bus

b08b1bde introduced a subtle bug. Despite not using D-Bus types directly,
the code used the SDL_USE_LIBDBUS definition set by SDL_dbus.h to conditionally
compile calls SDL_DBus_ScreensaverTickle() and SDL_DBus_ScreensaverInhibit().
As a result, it still compiled without SDL_dbus.h included, but screensaver
suspension silently failed to work.

The D-Bus stuff could probably use some tweaks to be harder to accidentally
break, but for now just restore the header includes.

src/video/wayland/SDL_waylandvideo.h

@@ -29,6 +29,7 @@
 #include "wayland-util.h"
 
 #include "../SDL_sysvideo.h"
+#include "../../core/linux/SDL_dbus.h"
 #include "../../core/linux/SDL_ime.h"
 
 struct xkb_context;

src/video/x11/SDL_x11video.h

@@ -56,6 +56,7 @@
 #include <X11/extensions/xf86vmode.h>
 #endif
 
+#include "../../core/linux/SDL_dbus.h"
 #include "../../core/linux/SDL_ime.h"
 
 #include "SDL_x11dyn.h"