(build_module_descriptor,add_objc_decls):

Set DECL_IN_SYSTEM_HEADER instead of TREE_USED on compiler-created decls.

From-SVN: r1493

gcc/objc/objc-act.c

@@ -885,8 +885,8 @@ build_module_descriptor ()
 
   finish_decl (_OBJC_MODULES_decl, init_module_descriptor (), NULLT);
 
-  /* Mark the decl as used to avoid "defined but not used" warning. */
-  TREE_USED (_OBJC_MODULES_decl) = 1;
+  /* Mark the decl to avoid "defined but not used" warning. */
+  DECL_IN_SYSTEM_HEADER (_OBJC_MODULES_decl) = 1;
 
   /* Generate a constructor call for the module descriptor. 
      This code was generated by reading the grammar rules
@@ -4246,7 +4246,7 @@ add_objc_decls ()
 				   build_tree_list (NULLT, objc_super_template), 0);
 
   /* this prevents `unused variable' warnings when compiling with `-Wall' */
-  TREE_USED (_OBJC_SUPER_decl) = 1;
+  DECL_IN_SYSTEM_HEADER (_OBJC_SUPER_decl) = 1;
 }
 
 /*