std::vector move assign patch

[Jonathan Wakely]

On 26/04/17 21:35 +0200, François Dumont wrote:
>I plan to propose this patch when back to stage 1. As it defaults 
>default and move constructor I wonder if it can make any change to the 
>generated code.

N.B. we are back in stage 1:
https://gcc.gnu.org/ml/gcc/2017-04/msg00084.html

But this change is a bit too disruptive, so let's wait until after the
GCC 7.1 release.