Support verifying IP Address SANs

[olix0r]

webpki does not currently implement IP address SAN validation, as described in briansmith/webpki#54. This makes webpki/rustls unusable in a variety of situations.

@ereslibre opened briansmith/webpki#260 to fix this issue, but it has not yet been reviewed.

[flavio]

Should this issue be closed? The PR has been merged

[djc]

Yup, that sounds about right.