UI CHANGE: Removal of left-to-right mode in gcalctool

["Robert Ancell" <robert ancell gmail com>]

Left to right mode has been removed from gcalctool in 5.23.6:
http://bugzilla.gnome.org/show_bug.cgi?id=500994

The result is the left-to-right and arithmetic menus from the view
menu are not present and the only calculator mode is arithmetic (as
was previously the default).