SAVEVM on accidential window close

[masinter]

The discussion on control-W reminded us of a desire to SAVEVM if the display system, XWindow, etc. got closed without an explicit (LOGOUT). See discussion starting with this:

Would it help to have maiko handle an error from the display subsystem (X or SDL) and do the savevm before exiting?

Originally posted by @nbriggs in https://github.com/Interlisp/medley/issues/1445#issuecomment-1841664583