bug#16133: 24.3; copy-file fails on chmod when copying to FAT filesystem

[Artem Chuprina]

Please describe exactly what actions triggered the bug, and
the precise symptoms of the bug.  If you can, give a recipe
starting from `emacs -Q':

Having org on ext4 filesystem with 0664 permission on org/work.org, and
c1 on FAT filesystem with file permissions 0075 (in fact, SD card on
Android system, so such strange permissions) I do

M-: copy-file("org/work.org" "c1/work.org" t)

and get an error

Debugger entered--Lisp error: (file-error "Doing chmod" "operation not
permitted" $
  copy-file("org/work.org" "c1/work.org" t)
  eval((copy-file "org/work.org" "c1/work.org" t) nil)
  eval-expression((copy-file "org/work.org" "c1/work.org" t) nil)
  call-interactively(eval-expression nil nil)

That's right, it cannot do a chmod, but it cannot do it there at all, so
there is no sense to fail here.

The problem does not exist in GNU Emacs 23.4.1
(arm-unknown-linux-gnueabihf) of 2013-07-01 on henze, modified by Debian

In GNU Emacs 24.3.1 (arm-unknown-linux-gnueabihf)
 of 2013-10-01 on hummel, modified by Debian
Configured using:
 `configure '--build' 'arm-linux-gnueabihf' '--build'
 'arm-linux-gnueabihf' '--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/24.3/site-l\
isp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.3/site-lisp:/usr/share/em\
acs/site-lisp'
 '--with-crt-dir=/usr/lib/arm-linux-gnueabihf' '--with-x=no'
 '--without-gconf' '--without-gsettings'
 'build_alias=arm-linux-gnueabihf' 'CFLAGS=-g -O2 -fstack-protector
 --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wall'
 'LDFLAGS=-Wl,-z,relro' 'CPPFLAGS=-D_FORTIFY_SOURCE=2''

Important settings:
  value of $LC_MESSAGES: C
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Fundamental

Recent input:
ESC : ( c o p y - f i l e
SPC " o r g / e m a c s . DEL DEL DEL DEL DEL DEL w
o r k . o r g " SPC " c 1 / w o r k . o r g " ) RET
C-]