[Bug libstdc++/83981] vector::resize(size_type) should not require T to be CopyInsertable when std=c++14

[dtrebbien at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83981

--- Comment #13 from Daniel Trebbien <dtrebbien at gmail dot com> ---
(In reply to Jonathan Wakely from comment #9)
> Also, if boost::optional had a noexcept move constructor it would work fine.
> This is a boost bug.
> 
> The part of the patch addressing PR 83982 seems right.

I have split out the part of the patch addressing PR 83982 and have attached
the reduced patch there.