- Generalise inplace callback (de)registration

- Generalise inplace callback (de)registration
- (de)register inplace callbacks for module id
- No unbound-control set_option for ECS options
- Deprecated client-subnet-opcode config option
- Introduced client-subnet-always-forward config option
- Changed max-client-subnet-ipv6 default to 56 (as in RFC)
- Removed extern ECS config options
- module_restart_next now calls clear on all following modules
- Also create ECS module qstate on module_event_pass event

git-svn-id: file:///svn/unbound/trunk@4092 be551aaa-1e26-0410-a405-d3ace91eadb9