core: Allow customization of Logger and LoggerFactory

Change-Id: I48a8217ab4cfb34ce2993f11a26266723d8d2923
Refs: #2433
diff --git a/core/logger-factory.cpp b/core/logger-factory.cpp
index b0ef3cd..483387f 100644
--- a/core/logger-factory.cpp
+++ b/core/logger-factory.cpp
@@ -1,11 +1,12 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2014  Regents of the University of California,
- *                     Arizona Board of Regents,
- *                     Colorado State University,
- *                     University Pierre & Marie Curie, Sorbonne University,
- *                     Washington University in St. Louis,
- *                     Beijing Institute of Technology
+ * Copyright (c) 2014-2015,  Regents of the University of California,
+ *                           Arizona Board of Regents,
+ *                           Colorado State University,
+ *                           University Pierre & Marie Curie, Sorbonne University,
+ *                           Washington University in St. Louis,
+ *                           Beijing Institute of Technology,
+ *                           The University of Memphis.
  *
  * This file is part of NFD (Named Data Networking Forwarding Daemon).
  * See AUTHORS.md for complete list of NFD authors and contributors.
@@ -20,10 +21,14 @@
  *
  * You should have received a copy of the GNU General Public License along with
  * NFD, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
- **/
+ */
 
 #include "logger-factory.hpp"
 
+#ifdef HAVE_CUSTOM_LOGGER
+#error "This file should not be compiled when custom logger is used"
+#endif
+
 namespace nfd {
 
 NFD_LOG_INIT("LoggerFactory");