x/net/ipv4,x/net/ipv6: add support for windows

[mikioh]

For now they are full of shims and spacers.

[gopherbot]

Comment 1:

CL https://golang.org/cl/97800043 mentions this issue.

[mikioh]

Comment 2:

We forgot to add both Getsockopt and Setsockopt functions into Go 1.3 syscall package.
So adding support for solaris would be Go 1.4.

[mikioh]

Comment 3:

This issue was updated by revision golang/net@38dcae4.

Fixes issue #7172.
LGTM=iant
R=golang-codereviews, gobot, iant
CC=golang-codereviews
https://golang.org/cl/97800043

[gopherbot]

Comment 4:

CL https://golang.org/cl/121880043 mentions this issue.