Mark msghdr.{_pad1, pad2} as pub

[jiangliu]

Mark msghdr.{pad1, pad2} as pub, so we could initialize a msghdr object.

[rust-highfive]

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[gnzlbg]

You can initialize this object by using mem::zeroed.

[jiangliu]

Thanks, I have solved my issue with the suggestion.
BTW, I don't know how to fix the failed test case, should I close this PR?