Undo limit variables in Emacs Manual

[Richard M. Stallman]

The variables undo-limit, undo-strong-limit and undo-outer-limit are
in basic.texi because that's where undo is documented, but they are
anything but basic.  I think they are important enough to be mentioned
in the manual.  I'd like to move their documentation to a different
place in the manual, but I am not sure where.

Can anyone suggest a good place?