Auto merge of #1144 - bitcartel:zc.v0.11.2.z7_tx_malleability_gettxid, r=bitcartel

A fix for transaction malleability

This PR fixes transaction malleability by not including the sigscript of transaction inputs and joinsplit sigs when hashing the txid.

This PR supercedes PR #1101 which was a minimal solution based on a new serialization flag.

This PR introduces GetTxid() to distinguish between getting a transaction id and the double sha256 hash.

The key changes are:
- Adding GetTxid() method to CTransaction which makes a copy of the transaction, clearing out the sigscript and joinsplitsig fields, before hashing.
- Verifying that every call to GetHash() actually wants a txid, and replacing with GetTxid().
- Renaming GetHash() to GetSerializeHash()
  - Rationale: In future, upstream code we want to merge will use GetHash() but we don't know the intent.  We should check to see if the intent is to receive a txid (most likely) in which case we replace with GetTxid(), or if upstream actually wants a double hash of the transaction we can use GetSerializeHash().
- Updated genesis data in chainparams.cpp

Note that coinbase transactions are excluded as they need the sigscript hashed to help avoid duplicate txids per BIP34:
  - This modification is related to a question from @ebfull on PR #1101 - "Can we think of a way this change allows us to construct two transactions with the same txid which can simultaneously appear in the blockchain? My guess is it would be possible to construct a coinbase transaction of such a form... this surely breaks invariants."

This PR Passes all tests in test_bitcoin (test data was updated in bloom_tests, miner_tests and script_tests).

src/miner.cpp

@@ -211,7 +211,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
             unsigned int nTxSize = ::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION);
             dPriority = tx.ComputePriority(dPriority, nTxSize);
 
-            uint256 hash = tx.GetHash();
+            uint256 hash = tx.GetTxid();
             mempool.ApplyDeltas(hash, dPriority, nTotalIn);
 
             CFeeRate feeRate(nTotalIn-tx.GetValueOut(), nTxSize);
@@ -255,7 +255,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
                 continue;
 
             // Skip free transactions if we're past the minimum block size:
-            const uint256& hash = tx.GetHash();
+            const uint256& hash = tx.GetTxid();
             double dPriorityDelta = 0;
             CAmount nFeeDelta = 0;
             mempool.ApplyDeltas(hash, dPriorityDelta, nFeeDelta);
@@ -302,7 +302,7 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
             if (fPrintPriority)
             {
                 LogPrintf("priority %.1f fee %s txid %s\n",
-                    dPriority, feeRate.ToString(), tx.GetHash().ToString());
+                    dPriority, feeRate.ToString(), tx.GetTxid().ToString());
             }
 
             // Add transactions that depend on this one to the priority queue