Add lifetime bounds on Items and MutItems.

[dschatzberg]

This also required a fix for Vec's MoveItems. This resolves issue #16941

[huonw]

It may be somewhat important for this to stay as pointers for non-zero sized types, since casting to integers loses optimisation information, e.g.

let end = if mem::size_of::<T>() == 0 {
     (p as uint + self.len()) as *const T
} else {
     p.offset(self.len() as int)
};

I would be very interested in seeing this not reencode the iteration, but I guess this may not be possible.

[dschatzberg]

Thanks for the response. I've gone ahead and made the change. My first pass at fixing this issue involved making an UnsafeItems struct which could be used to implement Items, MutItems, and Vec's MoveItems. But on second thought it seemed a bit unnecessary to create a new public struct which had very few uses.

If this is desirable, I'd be happy to implement it that way.

[aturon]

@huonw is this good to go?

[huonw]

Can you add a test for move_items specifically, including testing with both zero-sized and non-zero-sized types?

Thanks! (Sorry it's taken so long.)

[dschatzberg]

Looking at this now. I assume you want me to rebase to master which causes a few more things to break.

[dschatzberg]

I've updated the pull request to work off the latest commits. In the interim - this fix also affected the new btree implementation