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.
Lars Andersen <notifications@github.com> writes:

>> +(defcustom clojure-docstring-fill-prefix 2
>
> It's very hard to understand what this does. We should talk about the
> effect of the variable, and not just extracting a magic value from
> the implementation and giving it a name.

`clojure-docstring-fill-prefix-width' describes the option accurately.

> The vim plugin called this align-multiline-strings, and that is much
> better, I think, because it gives some clue as to what the effect of
> the variable is.

`align-multiline-strings' is not clear to me.  I guess it all depends
on whether you are accustomed to Emacs options names or Vim ones.