x11: Use XSync when changing window position instead of XFlush.
Attempt to fix regression in Bugzilla #4646.
diff --git a/src/video/x11/SDL_x11window.c b/src/video/x11/SDL_x11window.c
index 64bdb78..d5b7fd0 100644
--- a/src/video/x11/SDL_x11window.c
+++ b/src/video/x11/SDL_x11window.c
@@ -810,7 +810,7 @@
/*Attempt to move the window*/
X11_XMoveWindow(display, data->xwindow, window->x - data->border_left, window->y - data->border_top);
- X11_XFlush(display);
+ X11_XSync(display, False);
/*If the window is not moved, then the coordinates on the window structure are out of sync, so we
update them here. */
