They are not actually used.

Computing the material phase at a particular point may involve
a call to a Python function.  That is usually quite costly.
Therefore, make sure that this call is really made only once
per quadrature point.

Set up CI pipelines

See merge request dune-microstructure!1

Because such statements bleed into all the files that include
the headers, and this may lead to compilation errors later.

It is not needed, and it is not present on many platforms.