Update patch dumux.m4.

It is needed for external modules which depends
on dumux when used together with dune-common 2.2.
With dune 2.3 it is not needed anymore.
(reviewed by fetzer)


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@12537 2fb0f335-1f38-0410-981e-8018bf24f1b0