core: ignore non-Ethernet AF_LINK addresses when enumerating NICs.

Also modernize the code with some C++11 features.

Change-Id: Ibd29b39c37fdce8f87f917ab0cf48750e631e76c
diff --git a/core/network-interface.hpp b/core/network-interface.hpp
index c5296a1..8519db1 100644
--- a/core/network-interface.hpp
+++ b/core/network-interface.hpp
@@ -28,10 +28,10 @@
 
 #include "common.hpp"
 
-#include <net/if.h>
-
 #include <ndn-cxx/util/ethernet.hpp>
 
+#include <net/if.h>
+
 namespace nfd {
 
 namespace ethernet = ndn::util::ethernet;
@@ -88,7 +88,7 @@
   return (flags & IFF_UP) != 0;
 }
 
-std::list< shared_ptr<NetworkInterfaceInfo> >
+std::vector<NetworkInterfaceInfo>
 listNetworkInterfaces();
 
 } // namespace nfd