x11/vdesk: upgrading 1.2 -> 1.3
Major changes:
- Update the autotools build system.
- Ensure built cleanly with a compiler supporting any C version from ANSI C to C23
- Tidy up the code and documentation, and convert the ChangeLog to NEWS format
- Ensure that vdesk always calls XCloseDisplay before exiting
Event: Wiesbaden Hackathon 202604