patch 8.0.0557: GTK: using static gravities is not useful

Problem:    GTK: using static gravities is not useful.
Solution:   Remove setting static gravities. (Kazunobu Kuriyama)
diff --git a/src/gui_gtk_f.c b/src/gui_gtk_f.c
index 287a87e..bb4c632 100644
--- a/src/gui_gtk_f.c
+++ b/src/gui_gtk_f.c
@@ -92,11 +92,6 @@
 				    gboolean force_allocate);
 static void gtk_form_position_children(GtkForm *form);
 
-#if !GTK_CHECK_VERSION(3,16,0)
-static void gtk_form_set_static_gravity(GdkWindow *window,
-					gboolean use_static);
-#endif
-
 static void gtk_form_send_configure(GtkForm *form);
 
 static void gtk_form_child_map(GtkWidget *widget, gpointer user_data);
@@ -370,10 +365,6 @@
 #endif
     gdk_window_set_user_data(form->bin_window, widget);
 
-#if !GTK_CHECK_VERSION(3,16,0)
-    gtk_form_set_static_gravity(form->bin_window, TRUE);
-#endif
-
 #if GTK_CHECK_VERSION(3,0,0)
     {
 	GtkStyleContext * const sctx = gtk_widget_get_style_context(widget);
@@ -845,9 +836,6 @@
 #endif
 
 	gtk_widget_set_parent_window(child->widget, child->window);
-#if !GTK_CHECK_VERSION(3,16,0)
-	gtk_form_set_static_gravity(child->window, TRUE);
-#endif
 	/*
 	 * Install signal handlers to map/unmap child->window
 	 * alongside with the actual widget.
@@ -879,15 +867,6 @@
 {
     gtk_form_attach_child_window(form, child);
     gtk_widget_realize(child->widget);
-
-#if !GTK_CHECK_VERSION(3,16,0)
-    if (child->window == NULL) /* might be already set, see above */
-# if GTK_CHECK_VERSION(3,0,0)
-	gtk_form_set_static_gravity(gtk_widget_get_window(child->widget), TRUE);
-# else
-	gtk_form_set_static_gravity(child->widget->window, TRUE);
-# endif
-#endif
 }
 
     static void
@@ -999,16 +978,6 @@
 	gtk_form_position_child(form, tmp_list->data, FALSE);
 }
 
-#if !GTK_CHECK_VERSION(3,16,0)
-    static void
-gtk_form_set_static_gravity(GdkWindow *window, gboolean use_static)
-{
-    /* We don't check if static gravity is actually supported, because it
-     * results in an annoying assertion error message. */
-    gdk_window_set_static_gravities(window, use_static);
-}
-#endif /* !GTK_CHECK_VERSION(3,16,0) */
-
     void
 gtk_form_move_resize(GtkForm *form, GtkWidget *widget,
 		     gint x, gint y, gint w, gint h)
diff --git a/src/version.c b/src/version.c
index efb2ef3..d37033f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    557,
+/**/
     556,
 /**/
     555,