RE: abbreviate-file-name on Windows seems incorrect

["Drew Adams" <drew.adams@oracle.com>]

It seems that `abbreviate-file-name' does not recognize the effect of using
`setenv' inside Emacs (on Windows).

1. Outside Emacs, set $HOME to c:\ ("c:\\" as a Lisp string).

emacs -Q

(getenv "HOME") ; => "c:\\"
(setenv "HOME" "c:/drews-lisp-20/")
  ; => "c:/drews-lisp-20/"
(abbreviate-file-name "c:/drews-lisp-20/")
  ; => "c:/drews-lisp-20/" (EXPECTED "~/")

That is, I would expect $HOME to be replaced by ~/ (or perhaps ~), but it
was not.


2. Outside Emacs, set $HOME to c:\drews-lisp-20\.

emacs -Q

(getenv "HOME") ; => "c:\\drews-lisp-20\\"
(abbreviate-file-name "c:/drews-lisp-20/")
 ; => "~/"

(setenv "HOME" "c:/drews-lisp-20/")
  ; => "c:/drews-lisp-20/"
(abbreviate-file-name "c:/drews-lisp-20/")
  ; => "~/"

`directory-abbrev-alist' remained nil throughout both tests.