bug#1020: url-expand-file-name expands wrongly on Windows

[Klaus Straubinger]

In GNU Emacs 22.3.1 (i386-mingw-nt5.1.2600)
 of 2008-09-06 on SOFT-MJASON
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4)'

the problem described in
<http://lists.gnu.org/archive/html/bug-gnu-emacs/2008-03/msg00123.html>
still occurs.

  (url-expand-file-name "test" ["http" nil nil "www.gnu.org" 80 "/" nil nil t])

  --> "http://www.gnu.org/c:/test";;


  (url-http-expand-file-name
   [nil nil nil nil nil "test" nil nil nil]
   ["http" nil nil "www.gnu.org" 80 "/" nil nil t])

  --> "/c:/test"

url-http-expand-file-name is an alias for url-default-expander; this
could be changed.

But currently the function url-default-expander calls the function
expand-file-name while canonicalizing URLs. This is not a good idea on
Windows because there the drive letter will be inserted.