Fix safe iterator inconsistent assertion

[Jonathan Wakely]

On 21/06/18 07:36 +0200, François Dumont wrote:
>Working on iterator == operator I noticed that a comparison in 
>_Safe_iterator was inconsistent.
>
>Â Â Â  * include/debug/debug.h

Wrong filename in the ChangeLog here.

>Â Â Â  (_Safe_iterator<>(const _Safe_iterator<_MutableIterator,>& __x)):
>Â Â Â  Compare __x base iterator with a default initialized iterator of the
>Â Â Â  same type.

Please say value-initialized not default initialized (that's what
you're actually doing, and [forward.iterators] p2 only makes it
well-defined for value-initialized iterators).

OK with those changes to the ChangeLog, thanks.