Bump copyright dates.
diff --git a/lib/zip_source_commit_write.c b/lib/zip_source_commit_write.c
index 26c3dd7..67881f0 100644
--- a/lib/zip_source_commit_write.c
+++ b/lib/zip_source_commit_write.c
@@ -1,6 +1,6 @@
 /*
   zip_source_commit_write.c -- commit changes to file
-  Copyright (C) 2014 Dieter Baron and Thomas Klausner
+  Copyright (C) 2014-2018 Dieter Baron and Thomas Klausner
 
   This file is part of libzip, a library to manipulate ZIP archives.
   The authors can be contacted at <libzip@nih.at>