Update year in license files

In last year's update (D48219) it was suggested that the release manager
might want to do this, so here we go.

llvm-svn: 351194
GitOrigin-RevId: eb60fbfdb43cb8583eda1e338b3489ddef332f10
diff --git a/acxxel/LICENSE.TXT b/acxxel/LICENSE.TXT
index 547f6a4..9e71121 100644
--- a/acxxel/LICENSE.TXT
+++ b/acxxel/LICENSE.TXT
@@ -4,7 +4,7 @@
 University of Illinois/NCSA
 Open Source License
 
-Copyright (c) 2007-2018 University of Illinois at Urbana-Champaign.
+Copyright (c) 2007-2019 University of Illinois at Urbana-Champaign.
 All rights reserved.
 
 Developed by: