[v3, patch] Move std::list::_M_size closer to iterators

[Jonathan Wakely]

On 12/10/14 21:41 +0200, Marc Glisse wrote:
>Hello,
>
>this patch moves _M_size in std::list to a place where it should be 
>easier (no offsetof) to access from an iterator (it doesn't matter 
>when you access it from the main std::list object). It does not take 
>advantage of it yet, that can be done at any time, whereas the layout 
>will soon be fixed. This triggered one of the issues listed in PR 
>63345 (casting to a node* even for the sentinel), which I am fixing 
>here.

Nice, OK for trunk, thanks.