We had a feature that if you hit the down arrow key when you
were at the last message, it would recenter you. Waseem has bought
into temporarily removing this feature. Justifications:
1) We can always put it back.
2) Autoscrolling makes it less relevant.
3) The feature complicated the code a bit.
4) The feature worked different for End than down arrow, due to
a FIXME.
5) It might have been a misfeature for users that want more
control over their own scrolling.
6) You can achieve the same essential effect by using PgDn
or space.
(imported from commit fa6874bb5d29d7057bb1601f0b6d577bac1272c7)