RE: thunk.el: Document that thunk-force == funcall?

[Drew Adams]

> `thunk-force' is equivalent to `funcall' - thunks are functions.  I
> wonder if we could/should officially document that fact?
> 
> The background: because thunks are functions, one is allowed (and it is
> useful) to directly pass them to higher order functions e.g. as a test
> predicate, or bind them using `cl-flet', or `cl-letf' to a
> `symbol-function' place.  Currently, the official solution would
> require
> to use a lambda wrapper.
> 
> I have encountered this requirement several times (and using `thunk-
> let' was not always the solution) - thus my question.

FWIW, that makes sense to me.  Why not tell users this?
It's fine to have an abstraction, but in Lisp it can
help to know the implementation, especially in a
straightforward case like this.