Feature-sync boot() with other platforms: - run shutdown hooks. - do not turn reboot into halt if cold and invoked from ddb.
Feature-sync boot() with other platforms:
- run shutdown hooks.
- do not turn reboot into halt if cold and invoked from ddb.

ok deraadt@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars