More portable infrastructure for deprecating CPPFLAGS-like configure substitutes

[[Imported from SVN: r5808]]

m4/Makefile.am

@@ -5,6 +5,7 @@ ALLM4S = acx_blas.m4 acx_lapack.m4 acx_mpi.m4 acx_pthread.m4 \
          dune_autobuild.m4 dune_common.m4 dune_compiler.m4	\
 	 dune_cppincludeopt.m4					\
 	 dune_deprecated.m4					\
+	 dune_deprecated_cppflags.m4				\
          dune_docu.m4 dune_exprtmpl.m4  dune_linkcxx.m4 \
 	 dune.m4 \
          dune_mpi.m4 dune_streams.m4 \

m4/dune_deprecated_cppflags.m4

+dnl -*- autoconf -*-
+# Define configure substitution SUBSTITUTION.  Assign value to it but add an
+# additional preprocessor define which may be detected by config.h.  Add some
+# text to config.h which detects that define and issues the warning in
+# message.
+#
+# DUNE_DEPRECATED_CPPFLAGS(SUBSTITUTION, VALUE, MESSAGE)
+AC_DEFUN([DUNE_DEPRECATED_CPPFLAGS],
+[
+  AH_VERBATIM([DEPRECATED_$1_USED],
+[#ifdef DEPRECATED_$1_USED
+#warning $3
+#endif])
+  AC_SUBST([$1], [$2" -D DEPRECATED_$1_USED"])
+])

m4/dune_mpi.m4

@@ -170,7 +170,8 @@ AC_DEFUN([DUNE_MPI],[
     AC_SUBST(DUNEMPILDFLAGS, $DUNEMPILDFLAGS)
     AC_SUBST(DUNEMPILIBS, $DUNEMPILIBS)
 
-    AC_SUBST(MPI_CPPFLAGS, "$dune_mpicppflagswarn $DUNEMPICPPFLAGS")
+    DUNE_DEPRECATED_CPPFLAGS(MPI_CPPFLAGS, "$dune_mpicppflagswarn $DUNEMPICPPFLAGS",
+      [The MPI_CPPFLAGS configure substitute is deprecated.  Please change your Makefile.am to use DUNEMPICPPFLAGS instead.  Note that it is a good idea to change any occurance of MPI_LDFLAGS into DUNEMPILIBS and DUNEMPILDFLAGS as apropriate, since it is not possible to issue a deprecation warning in that case.])
     AC_SUBST(MPI_LDFLAGS, "$DUNEMPILDFLAGS $DUNEMPILIBS")
     AC_SUBST(MPI_VERSION, $dune_MPI_VERSION)
     AC_DEFINE(HAVE_MPI,ENABLE_MPI,[Define if you have the MPI library.
@@ -181,7 +182,8 @@ AC_DEFUN([DUNE_MPI],[
     AC_SUBST(DUNEMPILDFLAGS, "")
     AC_SUBST(DUNEMPILIBS, "")
 
-    AC_SUBST(MPI_CPPFLAGS, "$dune_mpicppflagswarn")
+    DUNE_DEPRECATED_CPPFLAGS(MPI_CPPFLAGS, "$dune_mpicppflagswarn",
+      [The MPI_CPPFLAGS configure substitute is deprecated.  Please change your Makefile.am to use DUNEMPICPPFLAGS instead.  Note that it is a good idea to change any occurance of MPI_LDFLAGS into DUNEMPILIBS and DUNEMPILDFLAGS as apropriate, since it is not possible to issue a deprecation warning in that case.])
     AC_SUBST(MPI_LDFLAGS, "")
   ])