LICENSE: Include information on uthash and MbedTLS

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2010--2019, Olaf Bergmann and others
+Copyright (c) 2010--2020, Olaf Bergmann and others
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
@@ -45,6 +45,14 @@ builds of the executables in the examples folder:
  * in the public domain.
  */
 
+========================================================================
+uthash
+
+libcoap uses uthash.h and utlist.h from Troy D. Hanson
+(http://troydhanson.github.com/uthash/). These files use the revised
+BSD license (BSD-1-Clause license) as included in these two source
+files.
+
 ========================================================================
 OpenSSL
 
@@ -68,3 +76,10 @@ When compiled with tinyDTLS support, this software includes components
 that are licensed under the terms of the Eclipse Distribution License 1.0
 (http://www.eclipse.org/org/documents/edl-v10.php).
 
+========================================================================
+MbedTLS
+
+When compiled with MbedTLS support, this software includes components
+that are licensed under the terms of the Apache 2.0 license
+(http://www.apache.org/licenses/LICENSE-2.0).
+