Log Message:
Import dhcpcd-6.9.0 with the following changes:
  *  Fix IPv6 prefix underflow when confirming deprecated but valid leases
  *  eloop.c and .h are now 100% portable outside of dhcpcd
     (provided the system supports recent POSIX and either you or
     the system provide working TAILQ macros)
  *  Allow waitip to work per interface.
  *  Handle ND options in the same way we handle DHCP and DHCPv6 options.
  *  Add new variable of type bitflags:flags where the flags ABCDEFGH,
     A is 10000000, B is 01000000, etc.
     Variables with the name reserved are no longer processed.
  *  Improve IN_IFF_TENTATIVE with ip sharing.