Remove excessive horizontal whitespace from hier(7) by correctly
using "-width". The http://mdocml.bsd.lv/mdoc/details/width.html
says: "Do not use macros in the argument specifying the width,
that's not portable. While GNU troff can handle it, mandoc cannot."
The same problem seems to exist in many other man pages.

Reviewed by: bapt, vangyzen
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D10238