Deleted Certificate Helper Functions

The following certificate helper functions were deleted after the SDR:

CertHelperVerifySignature - use CryptVerifyCertificateSignature

CertIsIssuerOfCRL - use CertCompareCertificateName

CertIsIssuerOfSubjectCertificate - use CertCompareCertificateName

CertGetPublicKey - use CryptExportPublicKeyInfo