usage: bbs [-s seclevel] [-l username] [-c conffile]

'seclevel' overwrites value from 'etc/users/', 'conffile' is a path to a
different 'bbs.conf' configuration file.

'bbsd' should not be started directly, 'bbs-guest' is self-explanatory.

A documentation for using 'bbs' is available online.

Sending SIGINT to bbsd let it dump its status into DUMPDIR (defined in
'local.h').
Sending SIGUSR1 to bbsd let it clean up its internal state if it is scrambeled
by an extraordinarily event (e.g. by SIGKILL killed bbs).
