MOVEONLY: non-consensus: from pow to chain:

- GetBlockProof
- GetBlockProofEquivalentTime

src/chain.h

@@ -282,6 +282,10 @@ public:
     const CBlockIndex* GetAncestor(int height) const;
 };
 
+arith_uint256 GetBlockProof(const CBlockIndex& block);
+/** Return the time it would take to redo the work difference between from and to, assuming the current hashrate corresponds to the difficulty at tip, in seconds. */
+int64_t GetBlockProofEquivalentTime(const CBlockIndex& to, const CBlockIndex& from, const CBlockIndex& tip, const Consensus::Params&);
+
 /** Used to marshal pointers into hashes for db storage. */
 class CDiskBlockIndex : public CBlockIndex
 {