Revert BDF copyright years.
diff --git a/src/bdf/bdflib.c b/src/bdf/bdflib.c
index 1fbb989..8e73f9f 100644
--- a/src/bdf/bdflib.c
+++ b/src/bdf/bdflib.c
@@ -1,6 +1,6 @@
 /*
  * Copyright 2000 Computing Research Labs, New Mexico State University
- * Copyright 2001-2018
+ * Copyright 2001-2014
  *   Francesco Zappa Nardelli
  *
  * Permission is hereby granted, free of charge, to any person obtaining a