[RFA/commit] Improve gdb_realpath for Windows hosts

[Eli Zaretskii]

> From: Joel Brobecker <brobecker@adacore.com>
> Cc: Joel Brobecker <brobecker@adacore.com>
> Date: Thu, 22 Dec 2011 21:14:44 +0400
> 
> gdb/ChangeLog:
> 
>         * utils.c (gdb_realpath): Add better support for Windows hosts.
> 
> Tested on x86-windows. Any objection to this?

Looks good to me.  Although there's a subtle semantic difference
between `realpath' on Posix platforms and GetFullPathName: the former
requires the file to exist, while the latter does not.  But I reckon
we handle this somewhere...

Did you test this with UNC file names?