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/m3quake.vim b/runtime/ftplugin/m3quake.vim
index 7762875..33ba633 100644
--- a/runtime/ftplugin/m3quake.vim
+++ b/runtime/ftplugin/m3quake.vim
@@ -1,7 +1,7 @@
 " Vim filetype plugin file
 " Language:	Modula-3 Quake
 " Maintainer:	Doug Kearns <dougkearns@gmail.com>
-" Last Change:	2022 June 12
+" Last Change:	2024 Jan 14
 
 if exists("b:did_ftplugin")
   finish
@@ -23,8 +23,12 @@
 endif
 
 if (has("gui_win32") || has("gui_gtk")) && !exists("b:browsefilter")
-  let b:browsefilter = "Modula-3 Quake Source Files (*.quake)\t*.quake\n" ..
-	\	       "All Files (*.*)\t*.*\n"
+  let b:browsefilter = "Modula-3 Quake Source Files (*.quake)\t*.quake\n"
+  if has("win32")
+    let b:browsefilter ..= "All Files (*.*)\t*\n"
+  else
+    let b:browsefilter ..= "All Files (*)\t*\n"
+  endif
   let b:m3quake_set_browsefilter = 1
   let b:undo_ftplugin ..= " | unlet! b:browsefilter b:m3quake_set_browsefilter"
 endif