The tresor_check tool became outdated back when the Tresor project was created
by re-writing its predecessor, the CBE, in C++. At this time, the check tool
was merely renamed but not updated. As there was also no autopilot test for the
tool, the tool remained outdated.
This commit rewrites the tool for the most recent Tresor version and adds an
autopilot test.
Ref #5062
