man pages up to mdoc guidelines and fix some minor formatting glitches.
Also fixed a number of man pages to not abuse the .Xr macro to
display functions and path names and a lot of other junk.
in the main text of various man pages.
Thanks to Warner Losh for adding an option to manck to allow
it to scan the entire man page looking for bogus xrefs, instead
of just checking the SEE ALSO section.
