Implement frame restacking under Android

* java/org/gnu/emacs/EmacsActivity.java (invalidateFocus1):
Synchronize with window.children for iteration through it.

* java/org/gnu/emacs/EmacsService.java (queryTree): Synchronize
with windowList for iteration through it.

* java/org/gnu/emacs/EmacsView.java (moveChildToBack): Correct
formatting mistake.
(moveAbove, moveBelow): New functions.

* java/org/gnu/emacs/EmacsWindow.java (destroyHandle, reparentTo)
(raise, lower): Remedy synchronization blunders.
(reconfigure): New function.

* src/android.c (android_init_emacs_window): Link with
`reconfigure'.
(android_reconfigure_wm_window): New wrapper function.

* src/androidfns.c (android_frame_restack): New function.
(Fandroid_frame_restack): Properly implement this function and
expunge outdated comment.

* src/androidgui.h (enum android_stack_mode)
(enum android_window_changes): New enumerators.

java/org/gnu/emacs/EmacsActivity.java

@@ -89,8 +89,11 @@ public class EmacsActivity extends Activity
     if (window.view.isFocused ())
       focusedWindow = window;
 
-    for (EmacsWindow child : window.children)
-      invalidateFocus1 (child);
+    synchronized (window.children)
+      {
+	for (EmacsWindow child : window.children)
+	  invalidateFocus1 (child);
+      }
   }
 
   public static void