message: Implement CSecureDataStream.
diff: #include "allocators.h"
  #include "keystore.h"
  #include "serialize.h"
  +#include "streams.h"
  class uint256;
  @@ -74,6 +75,18 @@ namespace wallet_crypto
  class TestCrypter;
  }
  +class CSecureDataStream : public CBaseDataStream<CKeyingMaterial>
  +{
  +public:
  + explicit CSecureDataStream(int nTypeIn, int nVersionIn) : CBaseDataStream(nTypeIn, nVersionIn) { }
  +
  + CSecureDataStream(const_iterator pbegin, const_iterator pend, int nTypeIn, int nVersionIn) :
  + CBaseDataStream(pbegin, pend, nTypeIn, nVersionIn) { }
  +
  + CSecureDataStream(const vector_type& vchIn, int nTypeIn, int nVersionIn) :
  + CBaseDataStream(vchIn, nTypeIn, nVersionIn) { }
  +};
  +
  /** Encryption/decryption context with key information */
  class CCrypter
  {
  