remove upstream support for Zen hobby OS

The new plan to support hobby operating systems is #3784.

And what kind of name is "Zen" anyway? There's already a
[Zen programming language](http://zenlang.sourceforge.net/)
and that's just confusing.
dcbd5ad155Andrew Kelley committed on 12/2/2019, 5:01:49 PMparentfc1373a
7 files changedLine totals unavailable