atf: Switch from std::auto_ptr<> to std::unique_ptr<>

[emaste]

Please make sure this also makes it into https://github.com/freebsd/atf/

[jhb]

Upstream has apparently fixed this differently using shared_ptr (not sure why, that seems wasteful and inefficient given there weren't any pointer assignments).

[emaste]

Upstream has apparently fixed this differently using shared_ptr

Huh, the only results for shared_ptr I see upstream are in NEWS claiming

Replace auto_ptr with std::shared_ptr (fixes modern C++ compliance).

But it's actually unique_ptr as in your review, from https://github.com/freebsd/atf/commit/f053ab687f6e27aa264f599ecbfc5ef27ad4e2d3
Pull request to update NEWS submitted: https://github.com/freebsd/atf/pull/103

[jhb]

Hah, cute. Ok then, that means I can still merge this and it will just fall out when doing our next vendor import.