bug#55386: 29.0.50; check-declare-directory doesn't work on Windows

[Eli Zaretskii]

> Cc: yasu@utahime.org, 55386@debbugs.gnu.org
> Date: Sat, 14 May 2022 12:09:56 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > (Hm...  it finds over a 100 in-tree declarations that it says are
> > malformed/wrong...  Perhaps somebody should have a look at that.)
> 
> Yes, please.

I've now fixed many of those.  The ones left are:

  . those from Org -- should be fixed in Org repository
  . references to packages not in core (like BBDB and W3M)
  . stuff that _looks_ like functions, but isn't: compiler-macros,
    constructors, games we play with setf etc. -- this is where
    check-declare "Needs Work"(TM) to be smarter

There are two warnings regarding PGTK which I didn't know what to do
about:

  lisp/frame.el:1996:Warning (check-declare): said ‘pgtk-frame-list-z-order’ was
      defined in src/pgtkfns.c: function not found

  lisp/term/pgtk-win.el:48:Warning (check-declare): said ‘pgtk-hide-emacs’ was
      defined in src/pgtkfns.c: function not found

Those functions indeed don't exist, AFAICT, but they _are_ called from
Lisp.  Po Lu, can you please DTRT there?