core: move NFD_VERSION{,_BUILD}_STRING to version.cpp

Change-Id: I97c23de24d8a176bb83a8f481f4880ff49ea710d
diff --git a/daemon/main.cpp b/daemon/main.cpp
index 83012fc..0675620 100644
--- a/daemon/main.cpp
+++ b/daemon/main.cpp
@@ -305,7 +305,7 @@
       "without WebSocket++";
 #endif
 
-  std::clog << "NFD version " NFD_VERSION_BUILD_STRING " starting\n"
+  std::clog << "NFD version " << NFD_VERSION_BUILD_STRING << " starting\n"
             << "Built with " BOOST_COMPILER ", with " BOOST_STDLIB
                ", " << boostBuildInfo <<
                ", " << pcapBuildInfo <<