bug#33664: 26.1; Document vars and functions in `cursor-sensor.el'

[Drew Adams]

To be clear: I don't really care about the "internal"
functions here.  I would like some doc for or
explanation of variable `cursor-sensor-inhibit',
particularly if the use of it by Isearch is part of
the design/intention.

(It also wouldn't hurt to add a doc string for
non-"internal" functions `cursor-sensor-tangible-pos'
and `cursor-sensor-move-to-tangible'.)