Fix "gfx print" in WIN32_USER_INTERFACE version by implementing Graphics_window_get_viewing_area_size. See https://tracker.physiomeproject.org/show_bug.cgi?id=1341
Fix "gfx print" in WIN32_USER_INTERFACE version by implementing Graphics_window_get_viewing_area_size.
See https://tracker.physiomeproject.org/show_bug.cgi?id=1341

cmiss/cmgui,cmiss/cmgui