move-only(ish): don't expose CCoinsViewDBCursor

No need for this to be a part of the header anymore.

Includes a small reference type style change.

src/txdb.cpp

@@ -168,6 +168,28 @@ bool CBlockTreeDB::ReadLastBlockFile(int &nFile) {
     return Read(DB_LAST_BLOCK, nFile);
 }
 
+/** Specialization of CCoinsViewCursor to iterate over a CCoinsViewDB */
+class CCoinsViewDBCursor: public CCoinsViewCursor
+{
+public:
+    CCoinsViewDBCursor(CDBIterator* pcursorIn, const uint256&hashBlockIn):
+        CCoinsViewCursor(hashBlockIn), pcursor(pcursorIn) {}
+    ~CCoinsViewDBCursor() {}
+
+    bool GetKey(COutPoint &key) const override;
+    bool GetValue(Coin &coin) const override;
+    unsigned int GetValueSize() const override;
+
+    bool Valid() const override;
+    void Next() override;
+
+private:
+    std::unique_ptr<CDBIterator> pcursor;
+    std::pair<char, COutPoint> keyTmp;
+
+    friend class CCoinsViewDB;
+};
+
 std::unique_ptr<CCoinsViewCursor> CCoinsViewDB::Cursor() const
 {
     auto i = std::make_unique<CCoinsViewDBCursor>(

src/txdb.h

@@ -70,28 +70,6 @@ public:
     void ResizeCache(size_t new_cache_size) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 };
 
-/** Specialization of CCoinsViewCursor to iterate over a CCoinsViewDB */
-class CCoinsViewDBCursor: public CCoinsViewCursor
-{
-public:
-    CCoinsViewDBCursor(CDBIterator* pcursorIn, const uint256 &hashBlockIn):
-        CCoinsViewCursor(hashBlockIn), pcursor(pcursorIn) {}
-    ~CCoinsViewDBCursor() {}
-
-    bool GetKey(COutPoint &key) const override;
-    bool GetValue(Coin &coin) const override;
-    unsigned int GetValueSize() const override;
-
-    bool Valid() const override;
-    void Next() override;
-
-private:
-    std::unique_ptr<CDBIterator> pcursor;
-    std::pair<char, COutPoint> keyTmp;
-
-    friend class CCoinsViewDB;
-};
-
 /** Access to the block database (blocks/index/) */
 class CBlockTreeDB : public CDBWrapper
 {