tools/tests: fix compilation errors caused by bind and placeholders

refs #2175

Change-Id: I65eadb0d0ccf468c3d478236335dbf09aa4dcc71
diff --git a/tools/nfdc.cpp b/tools/nfdc.cpp
index bfae684..2ecba4d 100644
--- a/tools/nfdc.cpp
+++ b/tools/nfdc.cpp
@@ -70,9 +70,7 @@
 
 namespace nfdc {
 
-using ndn::bind;
-using ndn::_1;
-using ndn::_2;
+using std::bind;
 
 const ndn::time::milliseconds Nfdc::DEFAULT_EXPIRATION_PERIOD = ndn::time::milliseconds::max();
 const uint64_t Nfdc::DEFAULT_COST = 0;