Move common sgsnemu/ggsn files to directory "lib"

Some files like in sgsnemu and ggsn directory where exactly the same.
They are now moved to the same directory for easier maintenance

Signed-off-by: Emmanuel Bretelle <chantra@debuntu.org>
diff --git a/ggsn/ggsn.c b/ggsn/ggsn.c
index 8b71884..57116ce 100644
--- a/ggsn/ggsn.c
+++ b/ggsn/ggsn.c
@@ -47,9 +47,9 @@
 
 #include <time.h>
 
-#include "tun.h"
-#include "ippool.h"
-#include "syserr.h"
+#include "../lib/tun.h"
+#include "../lib/ippool.h"
+#include "../lib/syserr.h"
 #include "../gtp/pdp.h"
 #include "../gtp/gtp.h"
 #include "cmdline.h"