More n3644 changes - forward_list and deque

[Joerg Sonnenberger]

On Tue, Aug 06, 2013 at 03:18:42PM -0400, Howard Hinnant wrote:
> Do you think debug mode would be more helpful, or less helpful, if the
> relational operators trapped a less-than comparison between two
> iterators i and j where i and j belong to two different vectors?

Does it ever make sense to put iterators into a std::map? I think it
does, so allowing relation operators would be sensible.

Joerg