conflicting definitions: SVN r333283 et al

Recent netdump changes appear to introduced/highlighted conflicting
definitions ..

Building /usr/obj/usr/src/i386.i386/lib/libsysdecode/ioctl.c
In file included from <stdin>:70:
In file included from
/usr/obj/usr/src/i386.i386/tmp/usr/include/netinet/netdump/netdump.h:37:
In file included from
/usr/obj/usr/src/i386.i386/tmp/usr/include/net/if.h:48:
/usr/obj/usr/src/i386.i386/tmp/usr/include/sys/socket.h:251:9: warning:
'AF_INET6' macro redefined [-Wmacro-redefined]
#define AF_INET6        28              /* IPv6 */
        ^
/usr/obj/usr/src/i386.i386/tmp/usr/include/netinet/ip_compat.h:1467:10:
note: previous definition is here
# define        AF_INET6        26
                ^
In file included from <stdin>:70:
In file included from
/usr/obj/usr/src/i386.i386/tmp/usr/include/netinet/netdump/netdump.h:37:
/usr/obj/usr/src/i386.i386/tmp/usr/include/net/if.h:58:10: warning:
'IFNAMSIZ' macro redefined [-Wmacro-redefined]
#define         IFNAMSIZ        IF_NAMESIZE
                ^
/usr/obj/usr/src/i386.i386/tmp/usr/include/netinet/ip_compat.h:1415:9:
note: previous definition is here
#define IFNAMSIZ                16
        ^
2 warnings generated.

	imb