const_iterator.cc: Tweak, avoid potential undefined behavior.

2013-07-05  Paolo Carlini  <paolo.carlini@oracle.com>

	* testsuite/23_containers/deque/modifiers/insert/const_iterator.cc:
	Tweak, avoid potential undefined behavior.
	* testsuite/23_containers/list/modifiers/insert/const_iterator.cc:
	Likewise.
	* testsuite/23_containers/vector/bool/modifiers/insert/
	const_iterator.cc: Likewise.
	* testsuite/23_containers/vector/modifiers/insert/const_iterator.cc:
	Likewise.

From-SVN: r200725