bibclean 2.16 (new formula)

* Build failed with superenv, hence included `env :std`.
* `ENV.deparallelize` was also necessary.
* Two `inreplace` statements insert `mkdir` statements needed on MacOS.
* One `inreplace` statement fixes the `mandir` variable in `Makefile`,
since it is not properly defined by autoconfig despite the `--mandir`
parameter passed to `./configure`.
@jacknagel if by "it" you mean the `bibcount` package, then no it doesn't. If you are referring to the formula, I am now working on a new commit with a wrapper script which moves the binary symlink away from `bin` and into `share`. If preferable, I can leave the symlink inside `bin` and add a `.old` extension to it.