Support of gdb for Windows 64 native systems

[Eli Zaretskii]

> Date: Sun, 14 Oct 2007 12:43:01 +0100
> From: Pedro Alves <pedro_alves@portugalmail.pt>
> CC: Eli Zaretskii <eliz@gnu.org>,  Kai.Tietz@onevision.com, 
>  gdb@sourceware.org
> 
> Nah, nah, na-na-naaah.  I've done it, and I said wouldn't  :)

Thanks!

> What's disabled:
> 	Use a shell to start the subprocess.

This will lose support for redirection.  Perhaps we could later add
something similar to what go32-nat.c did for DJGPP, to get that back.