add reasonable man page viewer

taken from hardcore-utils [0].
unlike busybox', this one supports specifying a section on the
command line, text formatting (bold, underline, etc), and does not
depend on 9base's nroff.

it's on par with gnu man, except that it doesnt support the groff
feature .TS/.TE, which allows embedding HTML-style tables in a
completely non-idiomatic, but idiotic way [1].
unfortunately this feature is even used by posix manpages,
for example man 1p printf.

closes #103

[0] https://github.com/rofl0r/hardcore-utils/
[1] http://www.podgrid.org/linux-bible/linux-bible-page607.html
remove man config used with busybox man (mostly just for the path)
remove man from busybox build