Catch up to current in src/external/bsd/dhcpcd/dist, requested
by roy in ticket #849:

external/bsd/dhcpcd/dist/Makefile              up to 1.1.1.5
external/bsd/dhcpcd/dist/src/arp.c              up to 1.1.1.7
external/bsd/dhcpcd/dist/src/auth.c            up to 1.1.1.5
external/bsd/dhcpcd/dist/src/auth.h            up to 1.1.1.3
external/bsd/dhcpcd/dist/src/bpf.c              up to 1.7
external/bsd/dhcpcd/dist/src/defs.h            up to 1.1.1.13
external/bsd/dhcpcd/dist/src/dhcp.c            up to 1.11
external/bsd/dhcpcd/dist/src/dhcp.h            up to 1.1.1.6
external/bsd/dhcpcd/dist/src/dhcp6.c            up to 1.1.1.12
external/bsd/dhcpcd/dist/src/dhcp6.h            up to 1.1.1.6
external/bsd/dhcpcd/dist/src/dhcpcd-definitions.conf up to 1.1.1.2
external/bsd/dhcpcd/dist/src/dhcpcd.8.in        up to 1.1.1.9
external/bsd/dhcpcd/dist/src/dhcpcd.c          up to 1.12
external/bsd/dhcpcd/dist/src/dhcpcd.conf.5.in  up to 1.1.1.9
external/bsd/dhcpcd/dist/src/if-bsd.c          up to 1.1.1.8
external/bsd/dhcpcd/dist/src/if-linux.c        up to 1.1.1.9
external/bsd/dhcpcd/dist/src/if-options.c      up to 1.10
external/bsd/dhcpcd/dist/src/ipv4ll.h          up to 1.1.1.4
external/bsd/dhcpcd/dist/src/ipv6.c            up to 1.1.1.10
external/bsd/dhcpcd/dist/src/ipv6.h            up to 1.1.1.7
external/bsd/dhcpcd/dist/src/ipv6nd.c          up to 1.1.1.8
external/bsd/dhcpcd/dist/src/ipv6nd.h          up to 1.1.1.6
external/bsd/dhcpcd/dist/src/route.c            up to 1.1.1.7
doc/3RDPARTY (manually modified)

Import dhcpcd 7.0.5b.

Changes:
* Routing: Fix case when cloning route changes but needs to be replaced
* DHCP6: Transpose DHCP userclass option into DHCP6
* DHCP6: Fix sending custom vendor class option
* Auth: Allow zero value replay detection data
* Auth: Allow different tokens for send and receive
* ND6: Warn if router lifetime is set to zero
* DHCP6: Softwire Address and Port-Mapped Clients, RFC7598
*  dhcp: Clarified some checksumming code, style and commentary
    (thanks to Maxime Villard)
*  dhcp6: IAID is now unique per IA type rather than global
*  ip6: if an IA callback causes a fork, exit earlier

(martin)