ArrayDeque: avoid triggering JDK 1.6 bug in tests

Use System.arraycopy instead of Arrays.copyOfRange to
avoid triggering JDK-7174363 bug in copyOfRange.

Fix package of ArrayDequeTest

libraries/stdlib/test/collections/ArrayDequeTest.kt

@@ -3,7 +3,7 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
-package collections
+package test.collections
 
 import test.collections.behaviors.iteratorBehavior
 import test.collections.behaviors.listIteratorBehavior