Check consensus hash consistency (RIPD-1456):

These changes use the hash of the consensus transaction set when
characterizing the mismatch between a locally built ledger and fully
validated network ledger. This allows detection of non-determinism in
transaction process, in which consensus succeeded, but a node somehow
generated a different subsequent ledger.

src/ripple/protocol/impl/STValidation.cpp

@@ -28,6 +28,7 @@ namespace ripple {
 
 STValidation::STValidation(
     uint256 const& ledgerHash,
+    uint256 const& consensusHash,
     NetClock::time_point signTime,
     PublicKey const& publicKey,
     NodeID const& nodeID,
@@ -36,6 +37,7 @@ STValidation::STValidation(
 {
     // Does not sign
     setFieldH256 (sfLedgerHash, ledgerHash);
+    setFieldH256 (sfConsensusHash, consensusHash);
     setFieldU32 (sfSigningTime, signTime.time_since_epoch().count());
 
     setFieldVL (sfSigningPubKey, publicKey.slice());
@@ -65,6 +67,11 @@ uint256 STValidation::getLedgerHash () const
     return getFieldH256 (sfLedgerHash);
 }
 
+uint256 STValidation::getConsensusHash () const
+{
+    return getFieldH256 (sfConsensusHash);
+}
+
 NetClock::time_point
 STValidation::getSignTime () const
 {