qtmir new FTBFS on Qt 5.7.1

[Timo Jyrinki]

See new build log at:

https://launchpadlibrarian.net/301149866/buildlog_ubuntu-zesty-amd64.qtmir_0.5.1+17.04.20161216-0ubuntu3~1_BUILDING.txt.gz

---
usr/include/miral/miral/set_window_managment_policy.h: In lambda function:
/usr/include/miral/miral/set_window_managment_policy.h:50:18: error: ‘make_unique’ is not a member of ‘std’
         { return std::make_unique<Policy>(tools, args...); }};
---
(etc)

https://wiki.ubuntu.com/Touch/QtTesting