Bug #54629 for Socket6: setsockopt SOL_IPV6-level constants (IPV6_*) missing from Socket6

The SOL_IPV6(=IPPROTO_IPV6)-level constants for setsockopt which are documented in ipv6(7) under Linux, many of which are common to other operating systems, are not defined by the Socket6 module, as they probably should. Of particular importance is IPV6_V6ONLY (common to many unices), which is indispensable for reliably binding an IPv6 socket to ip6addr_any (without setting the value of the IPV6_V6ONLY option, it is impossible to know whether the socket will bind to the IPv4 domain as well: under Linux, this depends on the net.ipv6.bindv6only sysctl which is unpredictable). The attached patch fixes the problem by adding the constants in question to those defined by Socket6. -- David A. Madore ( http://www.madore.org/~david/ )