bug#14295: Support copy-file ACLs for Solaris etc.

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 28 Apr 2013 23:15:06 -0700
> From: Paul Eggert <eggert@cs.ucla.edu>
> CC: bug-gnu-emacs@gnu.org
> 
> > How hard would it to support both?
> 
> I don't know, and I'd rather not support --without-acl.  This should
> have been an --enable/--disable option in the first place, as it's
> enabling or disabling a feature, not building with or without a
> package.  There's little point to Emacs departing from existing
> GNU practice here.

I just wonder how many people are used to that option.  Maybe not too
many, since this is a new feature.

> > This uses EOPNOTSUPP without #ifdef guards; is that universally
> > available?
> 
> Mostly, except for Windows, but to play it safe we can incorporate the
> Gnulib errno module, which defines EOPNOTSUPP if it's not already
> defined.

That almost works, but there are 2 issues:

 . I'd prefer to have the definition of EOPNOTSUPP in nt/inc/ms-w32.h,
   to make synchronization of config.nt with src/config.in easier.

 . More importantly, ENOTSUP is defined on Windows with the same value
   as ENOSYS (see ms-w32.h), so acl-errno-valid.c will fail to compile
   due to 2 identical case values in a switch.

> > If I'm right, perhaps it is best to leave the WINDOWSNT parts alone:
> 
> Sure, we can do that.

Thanks.

> OK.  Revised patch attached, which tries to address the above.

It looks fine, other than the 2 minor issues above, thanks.

> It relies on Gnulib for EOPNOTSUPP, except for WINDOWSNT where
> 'configure' isn't working yet, and there it adds a line to
> nt/config.nt to deal with this until we get 'configure' working.

'configure' is already working, I just need time to finish up the
branch and merge it.  But even when that is done (hopefully in a few
days), we will not immediately abandon the current configury.  It will
take some time.