bug#24484: 25.1; Wrong key for `dired-do-compress-to'

[Drew Adams <drew.adams@oracle.com>]

> > Emacs 25.1 devotes `c' to the new command
> > `dired-do-compress-to', unfortunately.
> >
> > Letter keys for`dired-do-*' commands are generally uppercase.
> > There are few exceptions: `k', `l', and `x'.
> >
> > Please consider using `M-z' or `K' (uppercase k) instead for
> > `dired-do-compress-to'.
> 
> The binding has now been in place for years, so I think it's too late
> to change now; closing.

That's not a good enough reason, IMO.  Emacs 25 is
not very old, and it's unlikely that changing the
_default_ binding of this command would impact users
negatively.

Keys involving character `c' are used, in Dired, for
"copy", "comment", and "change" (marks).  Keys for
compressing/uncompressing use char `z'.

And we use lowercase chars in Dired for other kinds
of things than `dired-do-*'.

In keeping with the use of char `z' for compressing
and uncompressing.  Dired+ uses `M-z' for
`dired-do-compress-to'.  I suggest that vanilla
Dired do likewise.