Add auth-type.

Sponsored by:	The FreeBSD Foundation
Make it possible to redefine portal-group "default".

Sponsored by:	The FreeBSD Foundation
Add a new auth-group "default", defaulting to deny, and make it possible
to redefine it.  From now on, assigning auth-group to a target is no longer
mandatory.

Sponsored by:	The FreeBSD Foundation
Update manual page to match recent auth-group "default" changes.

Sponsored by:	The FreeBSD Foundation
Use "default" as default discovery-auth-group, instead of "no-access".
It doesn't change visible behaviour, as previously auth-group "default"
wasn't redefinable, so by default access was always denied.

Sponsored by:	The FreeBSD Foundation
Use new auth-type "deny" instead of using "chap" with no chap entries;
it's cleaner this way, and gives better feedback to the user.

Sponsored by:	The FreeBSD Foundation
So, it turns out SIGCHLD is discarded by default, so we have to set up
a dummy handler to make it interrupt an ioctl(2) or select(2).

This makes those short-lived ctld(8) zombies disappear.

Sponsored by:	The FreeBSD Foundation
Improve error reporting.

Sponsored by:	The FreeBSD Foundation
Make ctld error out on invalid characters in ctl.conf.

Sponsored by:	The FreeBSD Foundation
Show proper configuration file line numbers in error messages.

Sponsored by:	The FreeBSD Foundation
Make the debug messages during ctld(8) shutdown less confusing.

Sponsored by:	The FreeBSD Foundation