Sync to head the following, requested by roy in ticket #1633:

        external/bsd/dhcpcd/dist/src/defs.h            up to 1.1.1.16
        external/bsd/dhcpcd/dist/src/dhcp.c            up to 1.13
        external/bsd/dhcpcd/dist/src/dhcp6.c            up to 1.1.1.13
        external/bsd/dhcpcd/dist/src/if-bsd.c          up to 1.1.1.9
        external/bsd/dhcpcd/dist/src/if.c              up to 1.1.1.9
        external/bsd/dhcpcd/dist/src/ipv4.c            up to 1.1.1.10
        external/bsd/dhcpcd/dist/src/ipv6.c            up to 1.1.1.12
        doc/3RDPARTY                                    (manually edited)

Import dhcpcd-7.0.8 with the following changes:
  *  Don't use IP_PKTINFO on NetBSD-7 as it's incomplete.
  *  Workaround RTM_NEWADDR sending the wrong broadcast address
    on NetBSD-7.
  *  Silence diagnostics if an address vanishes when reading
    it's flags on all BSD's.
  *  Misc compiler warnings fixed.

(martin)