File-name completer marks all files as executable on MS-Windows

[Eli Zaretskii <eliz@gnu.org>]

I discovered that completing on file names in GDB on MS-Windows marks
every file as executable.  This is because Readline uses 'access' and
X_OK to determine that, which doesn't work on Windows.

Suggested patch is below.

2014-12-27  Eli Zaretskii  <eliz@gnu.org>

	* complete.c (stat_char) [_WIN32]: Don't use 'access' and X_OK on
	Windows, they don't work.  Instead, look at the file-name
	extension to determine whether the file is executable.

--- readline/complete.c~0	2014-06-11 19:34:41.000000000 +0300
+++ readline/complete.c	2014-12-27 21:06:38.255053100 +0200
@@ -598,8 +598,21 @@ stat_char (filename)
 #endif
   else if (S_ISREG (finfo.st_mode))
     {
+#if defined (_WIN32) && !defined (__CYGWIN__)
+      /* Windows 'access' doesn't support X_OK and on latest Windows
+	 versions even invokes an invalid parameter exception.  */
+      char *ext = strrchr (filename, '.');
+
+      if (ext
+	  && (_rl_stricmp (ext, ".exe") == 0
+	      || _rl_stricmp (ext, ".cmd") == 0
+	      || _rl_stricmp (ext, ".bat") == 0
+	      || _rl_stricmp (ext, ".com") == 0))
+	character = '*';
+#else
       if (access (filename, X_OK) == 0)
 	character = '*';
+#endif
     }
   return (character);
 }