with the following changes:
- Allow configurations to be marked as Deprecated and Acivtated
- Harden resolvconf lock detection
If using resolvconf, dhcpcd-9.4.0 will require a resolvconf implementation
which supports the Deprecate option-C and Activate option-c
if the OS supports the concept of IP persistance.
Currently this is Linux (wireless roaming) and NetBSD-8 (IP persistance).
If there is no resolvconf then it works fine.
If there is a resolvconf which lacks these options then the
hook script will warn about an invalid option, but will otherwise work.
In this instance the DNS information cannot be Deprecated and may not
be optimal for multi-homed hosts.