Changes to 20man as of 9/2

Section 3.4.2:

^R redisplays input, not ^K (^K kills input).
^Z doesn't do anything.

Section 3.4:

The debugger will display all the relevant available history when entered
(it does the equivalent of an h command).  A non-nil argument to DEBUG can be
given to inhibit this, and on entry the debugger will do the equivalent
of an s command.