Creates the separator interface element. It shows a line between two menu items.
Ihandle* IupSeparator(void); [in C]
iup.separator{} -> (ih: ihandle) [in Lua]
separator() [in LED]
Returns: the identifier of the created element, or NULL if an error occurs.
The separator is ignored when it is part of the definition of the items in a bar menu.
In GTK uses GtkSeparatorMenuItem, in Windows uses InsertMenuItem, and in Motif uses xmSeparator.