array (array<>::_M_at): New.

2006-10-28  Paolo Carlini  <pcarlini@suse.de>
	
	* include/tr1/array (array<>::_M_at): New.
	(array<>::at): Fix off-by-one bug, use the above.
	* testsuite/tr1/6_containers/array/element_access/
	at_out_of_range.cc: Adjust.

	* include/tr1/array (class array<>): Remove non-conforming default
	for the second parameter.
	* include/ext/array_allocator.h: Adjust.

	* include/tr1/array (array<>::front, array<>::back): Do not return
	a reference to memory not belonging to the array when _Nm == 0.

From-SVN: r118114