update to latest documentation and update copyright year
diff --git a/configure.ac b/configure.ac
index 9d41d4c..4f44bde 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,4 +1,4 @@
-#  Copyright 1999-2020 ImageMagick Studio LLC, a non-profit organization
+#  Copyright 1999-2021 ImageMagick Studio LLC, a non-profit organization
 #  dedicated to making software imaging solutions freely available.
 #
 #  You may not use this file except in compliance with the License.  You may