Add support for encrypting spending keys

src/zcash/Address.cpp

@@ -1,9 +1,17 @@
 #include "Address.hpp"
 #include "NoteEncryption.hpp"
+#include "hash.h"
 #include "prf.h"
+#include "streams.h"
 
 namespace libzcash {
 
+uint256 PaymentAddress::GetHash() const {
+    CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
+    ss << *this;
+    return Hash(ss.begin(), ss.end());
+}
+
 uint256 ViewingKey::pk_enc() {
     return ZCNoteEncryption::generate_pubkey(*this);
 }