lib, zebra: unify link layer type and hardware address handling

lib, zebra: unify link layer type and hardware address handling

This removes the BSD specific usage of struct sockaddr_dl
hardware address. This unifies to use explict hw_addr member for
the address, and zebra specific enumeration for the link layer
type.

Additionally the zapi is updated to never send platform specific
structures over the wire, but the ll_type along with hw_addr_len
and hw_addr are now sent for all platforms.

Based on initial work by Paul Jakma.

Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
# Please enter the commit message for your changes. Lines starting
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# Author:    Timo Teräs <timo.teras@iki.fi>
#
# rebase in progress; onto 9c2f85d
# You are currently editing a commit while rebasing branch 'renato' on '9c2f85d'.
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# Changes to be committed:
#	modified:   isisd/isis_circuit.c
#	modified:   lib/if.c
#	modified:   lib/if.h
#	modified:   lib/zclient.c
#	modified:   zebra/interface.c
#	modified:   zebra/interface.h
#	modified:   zebra/kernel_socket.c
#	modified:   zebra/rt_netlink.c
#	modified:   zebra/rtadv.c
#	modified:   zebra/zserv.c
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# Untracked files:
#	"\033\033OA\033OB\033"
#	0001-bgpd-fix-build-on-Solaris.patch
#	ldpd/
#	redhat/ldpd.init
#	redhat/ldpd.service
#	tags
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