Refer to libtom license files

Author: mkj

LICENSE

@@ -8,7 +8,7 @@ The majority of code is written by Matt Johnston, under the license below.
 Portions of the client-mode work are (c) 2004 Mihnea Stoenescu, under the
 same license:
 
-Copyright (c) 2002-2015 Matt Johnston
+Copyright (c) 2002-2020 Matt Johnston
 Portions copyright (c) 2004 Mihnea Stoenescu
 All rights reserved.
 
@@ -32,7 +32,8 @@ SOFTWARE.
 
 =====
 
-LibTomCrypt and LibTomMath are written by Tom St Denis, and are Public Domain.
+LibTomCrypt and LibTomMath are written by Tom St Denis and others, see
+libtomcrypt/LICENSE and libtommath/LICENSE.
 
 =====