[Patch, regex, libstdc++/70745] Fix match_not_bow and match_not_eow

[Jonathan Wakely]

On 21/04/16 21:10 -0700, Tim Shen wrote:
>Bootstrapped and tested on x86-pc-linux-gnu debug.
>
>It is a conformance fix, but I don't think it's very important. I'm
>happy to backport it to gcc 5/4.9, but if it's not considered
>necessary, I'm Ok as well.

OK for trunk.

It is a small, safe change, so OK for the branches (6/5/4.9) too, but
let's wait a short while to make sure nobody finds any problems on
trunk (and gcc-6-branch is frozen for release right now anyway).

Thanks.