`checkoption` and `optstring` undocumented call to `checkstring` which calls `tolstring`.

[Duane Leslie <parakleta@...>]

`checkl?string` is documented to call `tolstring` with the associated
caveats, but `checkoption` and `optl?string` also call `checklstring`
and so the `tolstring` caveats also apply, but this is not in the
documentation.

Regards,

Duane.