ipv4: add support for solaris

This change adds support for Solaris.

To read and write IPv4 ancillary data using ControlMessage, ipv4 pacakge
requires https://go-review.googlesource.com/30171/

Note: Unlike other platforms, Solaris seems to have a few restrictions
on ICMP property access via raw IP sockets. At least applications are
prohibited from using IP_RECVTTL option for ICMP transport.

Fixes golang/go#17323.

Change-Id: Icb6dfa3c8eced28d14693ddfea4601301999d735
Reviewed-on: https://go-review.googlesource.com/30175
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/ipv4/genericopt_posix.go b/ipv4/genericopt_posix.go
index 53bc79f..f333581 100644
--- a/ipv4/genericopt_posix.go
+++ b/ipv4/genericopt_posix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd linux netbsd openbsd windows
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris windows
 
 package ipv4