Not installed headers are allowed to include ``config.h``. Cyclic include dependencies
prevent this, and must be avoided because of this. This is best guaranteed
by including every header in some source file as the first header,
-even before ``config.h``. This is partly enforced by :doc:`gmxtree`,
-which is run by Jenkins and votes accordingly in Gerrit.
+even before ``config.h``.
Code inside the library should not unnecessarily include headers. In
particular, headers should not include other headers if a forward