RX: Include netinet/ip6.h before inet/ip.h

RX: Include netinet/ip6.h before inet/ip.h

Some older Solaris (at least some Solaris 8) requires netinet/ip6.h to
be included before inet/ip.h, or the compiler chokes on some
ipv6-related declarations in inet/ip.h. So, include it.

Reviewed-on: http://gerrit.openafs.org/3662
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 9cc9b0d618ba1c787a8a684077c1d2f205b8889c)

Change-Id: Ic342a8ff9dc4c52c8f7178f103db93ba9bef6712
Reviewed-on: http://gerrit.openafs.org/3990
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>