work around itojun BSD IPV6_ONLY brokenness

socket/socket_tcp6.c

@@ -25,6 +25,12 @@ compat:
     } else
     return -1;
   }
+#ifdef IPV6_V6ONLY
+  {
+    int zero=0;
+    setsockopt(s,IPPROTO_IPV6,IPV6_V6ONLY,(void*)&zero,sizeof(zero));
+  }
+#endif
   return s;
 #else
   return socket_tcp4();

socket/socket_udp6.c

@@ -25,6 +25,12 @@ compat:
     } else
     return -1;
   }
+#ifdef IPV6_V6ONLY
+  {
+    int zero=0;
+    setsockopt(s,IPPROTO_IPV6,IPV6_V6ONLY,(void*)&zero,sizeof(zero));
+  }
+#endif
   return s;
 #else
   return socket_udp();