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`.
I don't think it's readable if you're not familiar with shell/sed/test/pipes. My main concern is if the output changes slightly or test fails in a future release it'll be hard to debug.