model: Bug fixes and small API change in ndn.cxx

ndn.cxx API need to be back-ported back, since it has important and not
very obvious problem.

Refs #1011 (http://redmine.named-data.net/issues/1011)
diff --git a/model/wire/ndnsim/wire-ndnsim.cc b/model/wire/ndnsim/wire-ndnsim.cc
index 8b4d81d..66c2c44 100644
--- a/model/wire/ndnsim/wire-ndnsim.cc
+++ b/model/wire/ndnsim/wire-ndnsim.cc
@@ -67,7 +67,7 @@
       uint8_t tmp[length];
       i.Read (tmp, length);
 
-      name->append (std::string (reinterpret_cast<const char*> (tmp), length));
+      name->append (tmp, length);
     }
 
   return name;