exposet multicast option functions which are used by the v6 code now.
more regen for complex and more.  only sun2 and ia64 missing now.
add a multicast test (what to do with v6?)
Succeed binding to multicast address for now: Open questions:
Open questions:

    http://mail-index.netbsd.org/tech-net/2014/07/23/msg004714.html
add multicast tests