* src/c++11/debug.cc
	(_Safe_iterator_base::_M_detach()): Reset state only if needed.
	(_Safe_iterator_base::_M_detach_single()): Likewise.
	(_Safe_local_iterator_base::_M_detach()): Reset state only if needed.
	(_Safe_local_iterator_base::_M_detach_single()): Likewise.

From-SVN: r261262