Add mapAnchors infrastructure to CCoinsView.

This adds the TXDB/CCoinsViewCache primitives necessary for
writing consensus rules for mapAnchors later.

src/txdb.h

@@ -14,6 +14,8 @@
 #include <utility>
 #include <vector>
 
+#include "libzerocash/IncrementalMerkleTree.h"
+
 class CBlockFileInfo;
 class CBlockIndex;
 struct CDiskTxPos;
@@ -34,10 +36,15 @@ protected:
 public:
     CCoinsViewDB(size_t nCacheSize, bool fMemory = false, bool fWipe = false);
 
+    bool GetAnchorAt(const uint256 &rt, libzerocash::IncrementalMerkleTree &tree) const;
     bool GetCoins(const uint256 &txid, CCoins &coins) const;
     bool HaveCoins(const uint256 &txid) const;
     uint256 GetBestBlock() const;
-    bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
+    uint256 GetBestAnchor() const;
+    bool BatchWrite(CCoinsMap &mapCoins,
+                    const uint256 &hashBlock,
+                    const uint256 &hashAnchor,
+                    CAnchorsMap &mapAnchors);
     bool GetStats(CCoinsStats &stats) const;
 };