bug#7784: executable-find does not find scripts on woe32

[Eli Zaretskii]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Cc: Sam Steingold <sds@gnu.org>, 7784@debbugs.gnu.org
> Date: Wed, 05 Jan 2011 15:24:26 +0100
> 
> One thing I noticed while experimenting with file-executable-p is that
> it returns false for files with extensions listed in PATHEXT. For
> instance, .JS is listed on one machine's PATHEXT but, after creating
> foo.js, (file-executable-p "foo.js") returns nil.
> 
> As those files are directly executable from the shell, maybe Emacs
> should recognize them as executables as well?

Patches for supporting PATHEXT are most welcome, TIA.