better alt hotkeys support

Created by: nick87720z

I noticed, that menubar displays menu hotkeys with underline, if any. Just like local window menu would do. However, pressing proper hotkey opens isolated popup menu, placed in window corner. Is not it possible, to handle it by global menus? Though it is different feature, but it seems to be rather expanded variant of #161 (closed) - there may be one method, which could open either specified menu item by hotkey, or default (first).