Menu help text not shown when using keyboard

[Lennart Borgman]

If you are using the keyboard to navigate the menus then you currently 
get no information about the help text that are associated with the menu 
entries. This help shows up only when you are using the mouse. From an 
accessibility point of view this is not very good.

I would suggest that this help texts where shown in the echo area 
whenever a a menu item is highlighted.