add NIST PKITS X.509 vectors

http://csrc.nist.gov/groups/ST/crypto_apps_infra/pki/pkitesting.html
http://csrc.nist.gov/groups/ST/crypto_apps_infra/documents/PKITS_data.zip
Merge pull request #1493 from reaperhulk/x509-test-vectors

add NIST PKITS X.509 vectors