Update referenced example to include unistd.h per manpage.
Update example to be more style(9)-ish, silence warnings and add
FreeBSD id to the source file.
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.