While here, also remove two forgotten descriptions for long obsolete
devices.

ok deraadt@ yasuoka@ reyk@

unused for now, but I plan to convert all programs in base to use it in
a future diff. /dev/bpf0 is for compatibility with existing binaries
and is to be removed after a transition period.
ok rpe krw, for the installer part
"Let's see it hit the tree." deraadt

and pwd_gensalt.c - so remove it from the default /etc/login.conf files as well.
ok millert@

OK dlg@ mpi@

flags in the disklabel. These flags were discarded in 2006.
Remove documentation for and instances of 'ty'. Add instances of
'dt' that were missing. Use 'floppy' as the value of 'dt' for all
floppies and 'rdroot' for all boot images/miniroots.
Add 'rdroot' to dktypenames and an associated #define DTYPE_RDROOT,
since 'dt' values are parsed by matching entries in dktypenames[].
Slightly tweaked part of larger cleanup diff previously ok deraadt@.

than the daemon class' default of 128.  Reminded by/ok ajacoutot@

ok henning@

in the install media. Reported by Donovan Watteau

ok deraadt millert

discussed with rpe and halex

spotted by Nathanael Rensen, thanks!

from Sylvestre Gallon ccna.syl gmail.com