Mostly manpage-shuffling according to the changes in the corrigendum,
wording changes and more idiomatic expressions.
All this is finished up by marking the POSIX 2013 conformant tools
with
.St -p1003.1-2013
which is not available in older mandoc builds or nroff, but which
reflects what we actually did, so who cares?
This is a huge step and it's not far until we can release sbase 0.1.
1) Shorten synopsis and reflect this in the manual
2) Use argv0 in usage()
3) Decrement argc in argv-loop for consistency
4) Make it clearer which error-code results from which errno in enprintf
5) Use idiomatic for-loop also for environ. Don't increment these pointers
in the loop itself!
- add .Os, it is mandatory.
- don't redeclare .Nm when it's not needed.
- fix some warnings (checked with mandoc -Tlint).
- remove some leftover old stuff.
