Bugfix: the implicit AMG tests now also compile with an unpatched PDELab. This is achieved by setting a corresponding macro in a PDELab header. This should be replaced by a proper configure test after the release. Reviewed by Christoph.

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@10350 2fb0f335-1f38-0410-981e-8018bf24f1b0