Remove deprecated diagonalmatrix.hh.

It was moved to dune-common in Dune 2.3.

dune/istl/CMakeLists.txt

@@ -10,7 +10,6 @@ install(FILES
    btdmatrix.hh
    bvector.hh
    colcompmatrix.hh
-   diagonalmatrix.hh
    gsetc.hh
    ilu.hh
    ilusubdomainsolver.hh

dune/istl/Makefile.am

@@ -9,7 +9,6 @@ istl_HEADERS = basearray.hh \
 	btdmatrix.hh \
 	bvector.hh \
 	colcompmatrix.hh \
-	diagonalmatrix.hh \
 	gsetc.hh \
 	ilu.hh \
 	ilusubdomainsolver.hh \

dune/istl/diagonalmatrix.hh

-// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
-// vi: set et ts=4 sw=2 sts=2:
-/*! \file
-   \brief  This file implements a quadratic diagonal matrix of fixed size.
-   \deprecated Use the corresponding file from dune-common instead!
- */
-
-#warning The file diagonalmatrix.hh has moved from dune-istl to dune-common,\
-  and will be removed from dune-istl after dune 2.3!
-#include <dune/common/diagonalmatrix.hh>