[multidomain] add patch that ensures compatibilty with Dune 2.4

The added patch multidomaingrid-2.3.patch adapts the
releases/2.3-branch of dune-multidomaingrid such that the 2.4 versions
of the Dune core modules can be used. See patches/README and
test/multidomain/README for details.

Reviewed by fetzer.



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@15379 2fb0f335-1f38-0410-981e-8018bf24f1b0