[IPV6]: Support several new sockopt / ancillary data in Advanced API (RFC3542).

Support several new socket options / ancillary data:
  IPV6_RECVPKTINFO, IPV6_PKTINFO,
  IPV6_RECVHOPOPTS, IPV6_HOPOPTS,
  IPV6_RECVDSTOPTS, IPV6_DSTOPTS, IPV6_RTHDRDSTOPTS,
  IPV6_RECVRTHDR, IPV6_RTHDR,
  IPV6_RECVHOPOPTS, IPV6_HOPOPTS

Old semantics are preserved as IPV6_2292xxxx so that
we can maintain backward compatibility.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 390d750..aa6eaf3 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -773,8 +773,7 @@
 	}
 	if (opt == NULL)
 		opt = np->opt;
-	if (flowlabel)
-		opt = fl6_merge_options(&opt_space, flowlabel, opt);
+	opt = fl6_merge_options(&opt_space, flowlabel, opt);
 
 	fl->proto = IPPROTO_UDP;
 	ipv6_addr_copy(&fl->fl6_dst, daddr);