Overhaul default menubar (still not perfect). * scripts/plot/figure.m: Always call __add_default_menu__. * scripts/plot/private/__add_default_menu__.m: Check that toolkit is FLTK before proceeding. Don't do redundant check that input is figure handle. Don't turn off handlevisibility for submenus, they are already hidden from above. Restrict findall() search to a depth of 1. Add __default_menu__ tags to Edit and Help menus so they can be identified. Don't call drawnow unnecessarily in callback routines. Use gcbf() so that Save filename is stored on a per figure basis rather than globally. Eliminate assigning to unused variables. Add HACK to turn off menubar if property is set to "none" on figure.