Revert patch 6505, I had committed it too quickly.

Since various compiler versions only support the 'unused'
attribute without a message, one has to check for both
versions separately.  Cf. the discussion in FS 956.

[[Imported from SVN: r6507]]

m4/dune_deprecated.m4

@@ -14,17 +14,13 @@ AC_DEFUN([DUNE_CHECKDEPRECATED],[
                     class t_peng { t_peng() {}; } DEP;
                     void foo() DEP;
                     void foo() {};],[],
-                                  [DUNE_DEPRECATED="__attribute__((deprecated))"
-                                   DUNE_DEPRECATED_MSG="__attribute__((deprecated(msg) ))"
-                     AC_MSG_RESULT(yes)],
-                                  [DUNE_DEPRECATED=""
-                                   DUNE_DEPRECATED_MSG=""
-                     AC_MSG_RESULT(no)])
+				   [DUNE_DEPRECATED="__attribute__((deprecated))"
+                    AC_MSG_RESULT(yes)],
+				   [DUNE_DEPRECATED=""
+                    AC_MSG_RESULT(no)])
+
+        AC_LANG_POP([C++])
 
-         AC_LANG_POP([C++])
- 
     AC_DEFINE_UNQUOTED(DUNE_DEPRECATED, $DUNE_DEPRECATED,
                       [how to create a deprecation warning])
-    AC_DEFINE_UNQUOTED(DUNE_DEPRECATED_MSG(msg), $DUNE_DEPRECATED_MSG,
-                      [how to create a deprecation warning with an additional message])
 ])