fw+table: workaround bogus doxygen warnings

Change-Id: I0a093658f4b27620ba9731a0640ca71c3d03360a
diff --git a/daemon/fw/forwarder.hpp b/daemon/fw/forwarder.hpp
index cad9396..373d395 100644
--- a/daemon/fw/forwarder.hpp
+++ b/daemon/fw/forwarder.hpp
@@ -251,7 +251,7 @@
   NetworkRegionTable m_networkRegionTable;
 
   // allow Strategy (base class) to enter pipelines
-  friend fw::Strategy;
+  friend ::nfd::fw::Strategy;
 };
 
 } // namespace nfd