bug#59804: shell-resync-dirs hangs in (t)csh

[Nicolas Graner <nicolas@graner.name>]

In a shell buffer where the running shell is csh or tcsh, the command
shell-resync-dirs never returns.

You can test this even without changing your normal shell by typing
`csh' in any shell buffer, then M-<RET>
Emacs hangs until you quit with C-g.

The reason is that the `dirs' command in (t)csh (unlike its equivalent
in bash) adds a trailing space to its output. This triggers an infinite
loop.

As evidence that the trailing space is the culprit, note that this
kludge, whiche removes it, fixes the problem:

(setq shell-dirstack-query "dirs | sed 's/ $//'")

-- Nicolas