runtime(ftplugin): Use "*" browsefilter pattern to match "All Files"

Problem:  The "*.*" browsefilter pattern only matches all files on
	  Windows (Daryl Lee)
Solution: Use "*" to filter on all platforms but keep "*.*" as the label
	  text on Windows. (Fixes #12685, Doug Kearns)

The *.* browsefilter pattern used to match "All Files" on Windows is a
legacy of the DOS 8.3 filename wildcard matching algorithm.  For reasons
of backward compatibility this still works on Windows to match all
files, even those without an extension.

However, this pattern only matches filenames containing a dot on other
platforms.  This often makes files without an extension difficult to
access from the file dialog, e.g., "Makefile"

On Windows it is still standard practice to use "*.*" for the filter
label so ftplugins should use "All Files (*.*)" on Windows and "All
Files (*)" on other platforms.  This matches Vim's default browsefilter
values.

This commit also normalises the browsefilter conditional test to check
for the Win32 and GTK GUI features and an unset b:browsefilter.

closes: #12759

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/ftplugin/qml.vim b/runtime/ftplugin/qml.vim
index fd5ddbb..aa05c11 100644
--- a/runtime/ftplugin/qml.vim
+++ b/runtime/ftplugin/qml.vim
@@ -2,6 +2,7 @@
 " Language: QML
 " Maintainer: Chase Knowlden <haroldknowlden@gmail.com>
 " Last Change: 2023 Aug 16
+" 	       2023 Aug 23 by Vim Project (browsefilter)
 
 if exists( 'b:did_ftplugin' )
    finish
@@ -14,10 +15,15 @@
 " command for undo
 let b:undo_ftplugin = "setlocal formatoptions< comments< commentstring<"
 
-if (has("gui_win32") || has("gui_gtk")) && !exists( 'b:browsefilter' )
+if (has("gui_win32") || has("gui_gtk")) && !exists("b:browsefilter")
    let b:browsefilter =
-      \ 'QML Files (*.qml,*.qbs)\t*.qml;*.qbs\n' .
-      \ 'All Files\t*\n'
+      \ "QML Files (*.qml, *.qbs)\t*.qml;*.qbs\n"
+   if has("win32")
+      let b:browsefilter .= "All Files (*.*)\t*\n"
+   else
+      let b:browsefilter .= "All Files (*)\t*\n"
+   endif
+   let b:undo_ftplugin .= " | unlet! b:browsefilter"
 endif
 
 " Set 'comments' to format dashed lists in comments.