[8] RFR JDK-8029788: Certificate validation- java.lang.ClassCastException

[Vincent Ryan]

Please review this fix to the OCSPResponse class in the internal
sun.security.provider.certpath package. Previously, when validating
an OCSP response, it expected the supplied issuer and/or trusted
responder X509 certs to already be in an internal format used by
the package. Now it accepts certs in any subclass of X509Certificate
and will convert to the internal format, if necessary.

Bug: https://bugs.openjdk.java.net/browse/JDK-8029788
Webrev: http://cr.openjdk.java.net/~vinnie/8029788/webrev.00/

This fixes a regression introduced by JDK-8015571.
Thanks.