bug#41147: A modern frame-title-format

[Lars Ljung]

I suggest that frame-title-format is changed to something like this:

(multiple-frames "GNU Emacs - %b"
                 ("GNU Emacs"))

This would give Emacs a slightly more modern look.

The current use of invocation-name might be useful for Emacs developers 
running multiple versions, but it serves no purpose for normal users.

The current use of system-name has no real value when running Emacs 
locally, but perhaps it could be added to remote frames only.

Kind regards,
Lars Ljung