Revision 1774562

On the ocsp-verification branch: Implement response parsing and verification.

* BRANCH-README: Update branch docs.

* serf_bucket_types.h
  (serf_ssl_ocsp_request_export): Update docstring.
  (serf_ssl_ocsp_response_parse
   serf_ssl_ocsp_response_verify): Update prototype and docstring.

* buckets/ssl_buckets.c
  (ocsp_response_status): New private helper function, extracted from ...
  (ocsp_callback): ... here, which uses it for response status checking.
  (ssl_ocsp_request_t): Replace the encoded server and issuer certificates
   with the OCSP certificate ID used to create requests and verify
   responses.
  (serf_ssl_ocsp_request_create,
   serf_ssl_ocsp_request_export,
   serf_ssl_ocsp_request_import): Update to match changed ssl_ocsp_request_t.
  (serf_ssl_ocsp_response_t): Change the type of the enclosed response.
  (free_ocsp_cert_id, free_ocsp_response): New; pool cleanup functions.
  (convert_asn1_generalized_time): New private helper function.
  (serf_ssl_ocsp_response_parse,
   serf_ssl_ocsp_response_verify): Update prototypes and implement.