Make header guards comply with Rule 3.2

refs: #3984

Change-Id: Iec7a0d9ff49cf6124af9e554432ee5f09a199651
diff --git a/nsync/sync-event.h b/nsync/sync-event.h
index 083ca61..a847431 100644
--- a/nsync/sync-event.h
+++ b/nsync/sync-event.h
@@ -20,8 +20,8 @@
  *         Alexander Afanasyev <alexander.afanasyev@ucla.edu>
  */
 
-#ifndef SYNC_EVENT_H
-#define SYNC_EVENT_H
+#ifndef NLSR_NSYNC_SYNC_EVENT_H
+#define NLSR_NSYNC_SYNC_EVENT_H
 
 #include "sync-common.h"
 
@@ -32,4 +32,4 @@
 
 } // Sync
 
-#endif // SYNC_EVENT_H
+#endif // NLSR_NSYNC_SYNC_EVENT_H