cf https://stackoverflow.com/questions/13980122/superfish-menu-display-subitems-left-if-there-is-not-enough-screenspace-on-the/47286812#47286812 https://jsfiddle.net/2hmeLw8g/5/ et https://jsfiddle.net/7j8m0yan/ Le code venant de https://gist.github.com/joeldbirch/5371649
