Do not shadow "it"

Just use a ranged for instead.

Author: tautschnig

src/cpp/cpp_typecheck_namespace.cpp

@@ -93,10 +93,7 @@ void cpp_typecheckt::convert(cpp_namespace_spect &namespace_spec)
   else
   {
     // do the declarations
-    for(cpp_namespace_spect::itemst::iterator
-        it=namespace_spec.items().begin();
-        it!=namespace_spec.items().end();
-        it++)
-      convert(*it);
+    for(auto &item : namespace_spec.items())
+      convert(item);
   }
 }