bug#21967: C-s insists on putting us back at the center of the screen

[Dan Jacobson]

Several taps of C-s get more and more of what we were searching for. All
well and good.

Two taps of C-l put the cursor at the top of the screen.

Several taps of C-s get more and more of what we were searching for. All
well and bad... because what if we want to stay at the top of the screen
while doing that... C-s insists on putting us back in the center of the
screen! (Which is usually good. However perhaps after two taps of C-l,
it should stay at the top during the next search or something.)