ping: refactor ping client to use a modular architecture

refs #2702

Change-Id: I0ee0403f84eaec35bdbf07af7b3bb52558113452
diff --git a/tools/ping/wscript b/tools/ping/wscript
index 406537b..0301eeb 100644
--- a/tools/ping/wscript
+++ b/tools/ping/wscript
@@ -5,7 +5,7 @@
     bld.program(
         features='cxx',
         target='../../bin/ndnping',
-        source='ndn-ping.cpp',
+        source=bld.path.ant_glob('client/*.cpp'),
         use='core-objects',
         )