Relicense to 0BSD, update mail address

I've come to the conclusion that copyright mostly just stands in the way
of software development.  In my jurisdiction I cannot give up my own
copyright and 0BSD seems to be the closest thing to public domain.

The updated mail address, also used in my author/committer lines,
is shorter and looks nicer.  People rarely interact anyway.

demo-json-rpc-server.c

@@ -1,11 +1,10 @@
 /*
  * demo-json-rpc-server.c: JSON-RPC 2.0 demo server
  *
- * Copyright (c) 2015 - 2016, Přemysl Janouch <p.janouch@gmail.com>
+ * Copyright (c) 2015 - 2018, Přemysl Janouch <p@janouch.name>
  *
  * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
+ * purpose with or without fee is hereby granted.
  *
  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF