make this copy as my personal development version

[[Imported from SVN: r1665]]

dune.module

 Module: dune-istl
-Version: 2.3-svn
+Version: 2.3-mn
 Maintainer: dune-devel@dune-project.org
 Depends: dune-common (>= 2.3)

m4/dune_istl.m4

 AC_DEFUN([DUNE_ISTL_CHECKS],
 [
+  AC_DEFINE(DUNE_ISTL_FLAVOR_MN, 1, [This is Martin's personal development version of dune-istl!])
+
   AC_REQUIRE([DUNE_PATH_PARMETIS])
   AC_REQUIRE([DUNE_PATH_SUPERLU])
   AC_REQUIRE([DUNE_PATH_SUPERLU_DIST])