bug#71223: 30.0.50; stack overflow after very fast opening and closing of frames

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> AFAIR, the waits are for 2 purposes:
>
>   . let the user of emacsclient see the error messages sent by the
>     server (because deleting the process clears the terminal);

In my patch these are mostly kept except they are short-circuited when
there's already some other emacsclient process filtering pending.
In practice this should rarely make a difference: you need to have at
least 3 more-or-less-concurrent emacsclients for the difference to show
up (the first is processed normally, and if there's no 3rd, then by the
time we process the second there's no other thing pending).

>   . let the server and the client have enough time to undo the
>     terminal settings they did when the session started, so that the
>     terminal is left in workable condition after the client exits.

These are kept in the form of timers instead of `sit-for`.

> The bug(s) in question should tell the details.

I don't know which bugs these are, sadly.
[ I must say I don't understand why we need to wait and then call
  `delete-process`.  ]


        Stefan