Import dhcpcd-8.0.4 with the following changes:

* BSD: Fixed router reachability tests
* inet6: If router unreachable, just solicit a new one
* inet6: Fon't install a default route if only lladdresses
* build: New make target import-src, only imports the bare essentials
* inet6: Stop listening to NA messages
* BSD: Listen to RTM_MISS messages
* DHCP: Fix in_cksum for Big Endian
* DHCP{,6}: Don't log an error if the lease file is truncated
* Solaris: Now fully supported!

(roy)