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

[jhb]

Summary

A few places were assigning auto_ptr<>s depending on the ownership
handoff. These now use an explicit std::move() as required by
unique_ptr<>.

[jhb]

A test VM is most of the way through a full kyua test run with this stack of changes applied and seems to be running fine.

Most of this change was mechanical (sed -e 's/auto_ptr/unique_ptr/') with a few places adjusted to use std::move() to fix compile errors.

[emaste]

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

[jhb]

Upstream PR: https://github.com/freebsd/kyua/pull/264