Needed by Lenovo USBRecoveryCreator.
-- v3: cryptxml/tests: Add some signature verification tests. cryptxml: Implement CryptXmlGetStatus(). cryptxml: Implement CryptXmlVerifySignature() stub. cryptxml: Partially implement CryptXmlGetSignature(). cryptxml: Partially implement CryptXmlGetDocContext(). cryptxml: Implement CryptXmlClose(). cryptxml: Implement CryptXmlOpenToDecode() stub.