[ndnSIM] core: Partial emulation of boost::asio::io_service for NS-3

This commit assumes that ndn::Scheduler is redirected to ns3::Simulator
routines inside the ndn-cxx library.

Change-Id: Ib987f09f76a5d2103365312261fc5a2eba7024d2
diff --git a/core/scheduler.hpp b/core/scheduler.hpp
index 3ad448b..a8bb94a 100644
--- a/core/scheduler.hpp
+++ b/core/scheduler.hpp
@@ -51,6 +51,9 @@
   eventId.cancel();
 }
 
+void
+resetGlobalScheduler();
+
 } // namespace scheduler
 } // namespace nfd