Fix the fullscreen window x11 message.

The l[3] is meant to be 1, and l[4] is meant to be 0, see:

https://specifications.freedesktop.org/wm-spec/wm-spec-latest.html#sourceindication

and

https://specifications.freedesktop.org/wm-spec/wm-spec-latest.html#idm45962883349936

to quote:

  window  = the respective client window
  message_type = _NET_WM_STATE
  format = 32
  data.l[0] = the action, as listed below
  data.l[1] = first property to alter
  data.l[2] = second property to alter
  data.l[3] = source indication
  other data.l[] elements = 0

Fixes #1358

Author: SiegeLordEx

src/x/xwindow.c

@@ -154,8 +154,8 @@ void _al_xwin_set_fullscreen_window(ALLEGRO_DISPLAY *display, int value)
 
    xev.xclient.data.l[1] = X11_ATOM(_NET_WM_STATE_FULLSCREEN);
    xev.xclient.data.l[2] = 0;
-   xev.xclient.data.l[3] = 0;
-   xev.xclient.data.l[4] = 1;
+   xev.xclient.data.l[3] = 1;  /* 1 = normal application source */
+   xev.xclient.data.l[4] = 0;
 
    XSendEvent(
       x11,