Implement `restart-emacs' on Android

* java/org/gnu/emacs/EmacsService.java (restartEmacs): New
function.
* src/android.c (struct android_emacs_service)
(android_init_emacs_service): Add new method.
(android_restart_emacs): New function.
* src/android.h: Update prototypes.
* src/emacs.c (Fkill_emacs): Call android_restart_emacs whenever
appropriate.

java/org/gnu/emacs/EmacsService.java

@@ -611,4 +611,16 @@ public class EmacsService extends Service
 
     return manager.thing;
   }
+
+  public void
+  restartEmacs ()
+  {
+    Intent intent;
+
+    intent = new Intent (this, EmacsActivity.class);
+    intent.addFlags (Intent.FLAG_ACTIVITY_NEW_TASK
+		     | Intent.FLAG_ACTIVITY_CLEAR_TASK);
+    startActivity (intent);
+    System.exit (0);
+  }
 };