(Info-mode): Doco fix.

(Info-mode): Doco fix.
(Info-next-preorder): Renamed from Info-next-preorder-1.
Old definition deleted.
After moving up, go to end of node.
(Info-last-preorder): If no menu, try the previous node.
After going down thru menu or to previous, position at end
of node and recenter.
After moving up, position at start of menu.
(Info-follow-nearest-node, Info-mouse-follow-nearest-node):
Use Info-next-preorder.
(Info-scroll-up, Info-scroll-down): Doc fix.