bug#37438: Hold down CTRL+L

[積丹尼 Dan Jacobson]

(C-l runs the command recenter-top-bottom.)
Hold down CTRL+L. What do you see?
Could this perhaps be rate-limited?
Holding down CTRL+K works fine (eating text at a pleasant pace)
but mistakenly holding down CTRL+L instead just creates an eerie
confusing effect.

In fact how about having it stop on the third CTRL+L, after which it
makes no sense anyway.

If the user wants to send more CTRL+L, have them lift their finger first.
emacs-version "26.1"