XPuniqName()
   Return name for a unique file
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   Function:   XPuniqName()

               This function uses a DOS call to create a file that is
               truly unique. You can be sure that the file name can be
               used by your application without bothering if you have
               overwritten another file (from another user). It's an easy
               way to overcome well known network problems. The functions are
               not network specific, and work in any situation (standalone,
               any network (should)).

               Contrary to XPtempName(), you have NO control over the name of
               the Temporary file to create. But then, you needn't bother
               about the name at all.

   Syntax:     XPuniqName([cDir][,nAttrib]) --> cUniName

   Arguments:  <cDir> is the directory to create the file, it
               defaults to current directory. nAttrib is optionnal and
               indicates the Attribute of the file to create, it defaults
               to 0.

   Returns:    the Name of the temporary file, or "" when an Error
               occured. In case of Error, inspect to XPferror()
               to see what the error was. Possibly Acces denied (5),
               or Path not found (3), for instance.

               The file name may contain any kind of characters.

               The file created is closed (zero lengtgh), and can be safely
               used by your application. It's name is thus returned.
               Use XPfunique() when you want the file to remain open.

   Usage:      cUniName := XPuniqName()