NTPd fails to build with MKINET6=no

[Scott Ellis <scotte%intrepid.warped.com@localhost>]

The build fails with:

--- dependall-ntp ---
ntp_intres.o: In function `ntp_intres':
ntp_intres.c:(.text+0x10fc): undefined reference to `in6addr_any'
ntp_intres.c:(.text+0x110a): undefined reference to `in6addr_any'
ntp_io.o: In function `is_wildcard_addr':
ntp_io.c:(.text+0x458): undefined reference to `in6addr_any'
ntp_io.o: In function `io_open_sockets':
ntp_io.c:(.text+0x3ae7): undefined reference to `in6addr_any'
ntp_io.c:(.text+0x3af3): undefined reference to `in6addr_any'
/nbu/source/netbsd/src/obj.amd64/nbu/source/netbsd/src/external/bsd/ntp/lib/libi
scntp/libiscntp.a(netaddr.o):netaddr.c:(.text+0x6bf): more undefined 
references
to `in6addr_any' follow
collect2: ld returned 1 exit status
*** [ntpd] Error code 1

nbmake: stopped in /nbu/source/netbsd/src/external/bsd/ntp/bin/ntpd

Not sure where PLATFORM_HAVEIPV6 is getting defined, but that looks like 
the culprit.

        ScottE