AddLine()

          Adds a line to a submenu as a no selectionable item

    Syntax:

         AddLine( aMenu, nSubMenu [, nPos] ) -> Nil

         aMenu    : The menu created with NewMenu()
         nSubMenu : The submenu's number where add the line
         nPos     : The line position in the submenu,
                    last position if null.

    Description:

         Adds a line to a submenu activing the item as a non selectionable
         item during all the process.

    Return:

         Nothing.

    Example:

         aMenu := NewMenu( { "^System", "^Tools", "^Other" }, ;
                           { "N/W", "R/W", "W/B",  "W+/B", ;
                             "N/W", "W/B", "N+/W", "R/W", "GR+/B" } )
         AddItem ( aMenu, 1, "Item ^1", "Message 1" )
         AddItem ( aMenu, 1, "Item ^2", "Message 2" )

         AddLine ( aMenu, 1, 2 )  // add a line between both items.