bug#22578: 24.5; dired-do-chmod on . or .. directories

[Kevin Ryde]

It'd be good if dired "M" `dired-do-chmod' could act on the "." and ".."
directories in the dired buffer.

As far as I can tell there'd be no reason they shouldn't.  I struck this
wanting to add write permission to a directory which had been left
read-only (something out of an unzip or untar).

(Presently dired-do-chmod also queries for the mode before announcing it
won't act on . or .., whereas of course usually in other places in emacs
such failing pre-conditions are checked before user input.)


In GNU Emacs 24.5.1 (i586-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2016-01-23 on x86-csail-01, modified by Debian
Configured using:
 `configure --build i586-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
 --build i586-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
 --libexecdir=/usr/lib --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
 --with-x=yes --with-x-toolkit=lucid --with-toolkit-scroll-bars
 --without-gconf --without-gsettings 'CFLAGS=-g -O2
 -fstack-protector-strong -Wformat -Werror=format-security -Wall'
 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'