Using the Sutherland-Hodgman algorithms convex and concave subject polygons can be clipped
by convex clip polygons.
For now we only need clipping to rectangles (Box), so limit our implementation to that. If needed this can be
trivially extended to convex clip polygons (a check whether the clip polygon is actually convex has to be added).
If convex clip polygons are needed we have to switch to e.g the Vatti algorithm.
Use -DCMAKE_BUILD_TEST_SUITE=1 during CMake invocation to activate building the tests.
The 'tests' target builds the unit tests which can then be executed using the 'test' target.
We depend on the Catch2 version of the system.
Since development normally takes place on current OSs, this shouldn't pose a problem.