File Owner and Group ID on Windows

[Eli Zaretskii]

I've just committed a series of changes, mainly to w32-specific files,
but also to dired.c, to query the w32 filesystems and report the owner
and group of every file.  (Up till now, Emacs on Windows would
attribute all the files to the user who was running the Emacs
session.)  This affects file-attributes,
directory-files-and-attributes, and Dired.

These changes required incompatible changes in `struct stat', so
please remove all *.o files (in src/oo-spd/i386/ and in
lib-src/oo-spd/i386/) before saying "make".

There could be some fallout, especially in code that was working until
now because all files appeared to be owned by the current user.  Now
this will change, which could cause Emacs think the user is trying to
change files she doesn't own.  VC is one place where such problems
could happen.  I'm asking Windows users to please be alert and report
any problems that could be related to this.

To temporarily work around any problems you bump into, you can set
w32-get-true-file-attributes to nil.

The new code needs some optimization, especially for networked drives;
I will add SID caching to do that.  Again, if you find Emacs too
sluggish, set w32-get-true-file-attributes to nil until performance
improves.

Note that lib-src programs now use our own version of `stat' as well
(this couldn't be avoided, due to incompatible layouts of `struct
stat'), so any problems with file accessibility from those programs
could also be due to some snafu I failed to resolve.  The version of
`stat' used by lib-src is much simpler and doesn't bother to look for
true file owner or even compute the inode, but any bugs I left there
could cause failures in previously working workflow.

Thanks.