core: Adding workaround for missing <byteswap.h> on FreeBSD

This commit also fixes a couple of compilation issues with gcc 4.2.1

Change-Id: Iacc5a742b666849694b6ee947482e78340f74336
diff --git a/tools/ndn-autoconfig-server.cpp b/tools/ndn-autoconfig-server.cpp
index ac5c3bf..f09a39a 100644
--- a/tools/ndn-autoconfig-server.cpp
+++ b/tools/ndn-autoconfig-server.cpp
@@ -51,7 +51,7 @@
   onInterest(const Name& name, const Interest& interest)
   {
     ndn::Data data(ndn::Name(interest.getName()).appendVersion());
-    data.setFreshnessPeriod(time::hours(1)); // 1 hour
+    data.setFreshnessPeriod(ndn::time::hours(1)); // 1 hour
 
     // create and encode uri block
     Block uriBlock = dataBlock(tlv::nfd::Uri,