Display local help in the echo area.
This displays a short help message, namely the string produced by
the `kbd-help' property at point. If `kbd-help' does not produce
a string, but the `help-echo' property does, then that string is
printed instead.
A numeric argument ARG prevents display of a message in case
there is no help. While ARG can be used interactively, it is
mainly meant for use from Lisp.
(fn &optional ARG)