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.
2 Added optional excessive login logging.
3) Added login acces control on a per host/tty base.
4) See skey(1) for skey descriptions and src/usr.bin/login/README
for the logging and access control features.
-Guido
