menu extension arrows should be on left when menu extends to left

[Drew Adams]

If you have a menu that is close to the right side of the display (e.g. Help
menu), then submenus open to the left of the main menu, not the right.

However, the small arrow (triangle) that indicates that a menu item
represents a submenu is always on the right. This means that it's hard to
see (notice) the arrow in this context.

The arrows should be on the left whenever the submenus will open to the
left.