OCSP stapling support

[p-mongo]

I am working on OCSP stapling support in MongoDB Ruby driver.

Per ruby/openssl#295 this functionality is currently not provided by MRI's openssl extension.

I have an open PR for MRI adding the support.

From a quick inspection of JRuby source I believe JRuby doesn't implement the required parts either (one needs to set the status extension on the tls context prior to connection and then provide the status callback that is used during connection establishment to verify the stapled response).