multiview: screen redraw to be set outside the redraw function
multiview: wm_draw: making area->do_draw = FALSE outside the main
function (for stereo draw function).

It's not entirely working though (see XXX in code).
multiview: SCREEN_OT_clean_full_area and WM_OT_stereo_toggle
1) removed the shortcut for SCREEN_OT_clean_full_area
2) created an operator to toggle the stereo option (per window)
   current shortcut: DKEY

Note: SCREEN_OT_clean_full_area and "Show/Hide Header Menus" need shortcuts