clojure-mode.el (clojure-docstring-fill-prefix): New option

* clojure-mode.el (clojure-docstring-fill-prefix): New option.

See https://github.com/clojure-emacs/clojure-mode/issues/241 for a discussion about this.
Bozhidar Batsov <notifications@github.com> writes:

> I'd suggest naming this clojure-docstring-fill-prefix-width.

Done in lastest PR.