hello: move constructor definition to implementation file.

Change-Id: Ia176b5cad081a61368f45ac137dc6c9474101751
refs: #4334
diff --git a/src/hello-protocol.cpp b/src/hello-protocol.cpp
index afbd564..4a3d06b 100644
--- a/src/hello-protocol.cpp
+++ b/src/hello-protocol.cpp
@@ -32,6 +32,12 @@
 const std::string HelloProtocol::INFO_COMPONENT = "INFO";
 const std::string HelloProtocol::NLSR_COMPONENT = "NLSR";
 
+HelloProtocol::HelloProtocol(Nlsr& nlsr, ndn::Scheduler& scheduler)
+  : m_nlsr(nlsr)
+  , m_scheduler(scheduler)
+{
+}
+
 void
 HelloProtocol::expressInterest(const ndn::Name& interestName, uint32_t seconds)
 {