[v3 PATCH] Implement C++17 variable templates for type traits.

[Jonathan Wakely]

On 29/07/16 01:27 +0300, Ville Voutilainen wrote:
>    Implement C++17 variable templates for type traits.
>    * include/std/chrono (treat_as_floating_point_v): New.
>    * include/std/ratio: (ratio_equal_v, ratio_not_equal_v)
>    (ratio_less_v, ratio_less_equal_v, ratio_greater_v)
>    (ratio_greater_equal_v): Likewise.

There's one overlong line in <ratio>, please split across two lines.

Apart from that it's fine - please go ahead and commit.

Thanks for doing all this C++17 work. As you mentioned on IRC we'll
need to update the status tables in the manual and the GCC 7 release
notes, but I can take care of that.