Bump automatic replay protection to May 2019 upgrade

Summary:
This returns main chain to ForkID of 0 after the Nov 2018
upgrade, and implements automatic replay protection for
the May 2019 upgrade.

For reference see last HF:
https://reviews.bitcoinabc.org/D1199

Test Plan:
Replay protection is covered by unit tests, however
it is very important to manually double check that the timestamp
for activation is set correctly.

Reviewers: deadalnix, schancel, jasonbcox, #bitcoin_abc

Reviewed By: deadalnix, schancel, jasonbcox, #bitcoin_abc

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1612

doc/release-notes.md

@@ -8,3 +8,5 @@ This release includes the following features and fixes:
  - Remove the rules, vbavailable and vbrequired result from the getblocktemplate RPC call.
  - Remove the rules argument from the getblocktemplate RPC call.
  - Log difference between block header time and received time when competing blocks are received for the same chain height.
+ - Bump automatic replay protection to May 2019 upgrade
+

src/chainparams.cpp

@@ -131,6 +131,9 @@ class CMainParams : public CChainParams {
         // Nov 15, 2018 hard fork
         consensus.magneticAnomalyActivationTime = 1542300000;
 
+        // Wed, 15 May 2019 12:00:00 UTC hard fork
+        consensus.greatWallActivationTime = 1557921600;
+
         /**
          * The message start string is designed to be unlikely to occur in
          * normal data. The characters are rarely used upper ASCII, not valid as
@@ -300,6 +303,9 @@ class CTestNetParams : public CChainParams {
         // Nov 15, 2018 hard fork
         consensus.magneticAnomalyActivationTime = 1542300000;
 
+        // Wed, 15 May 2019 12:00:00 UTC hard fork
+        consensus.greatWallActivationTime = 1557921600;
+
         diskMagic[0] = 0x0b;
         diskMagic[1] = 0x11;
         diskMagic[2] = 0x09;
@@ -423,6 +429,9 @@ class CRegTestParams : public CChainParams {
         // Nov 15, 2018 hard fork
         consensus.magneticAnomalyActivationTime = 1542300000;
 
+        // Wed, 15 May 2019 12:00:00 UTC hard fork
+        consensus.greatWallActivationTime = 1557921600;
+
         diskMagic[0] = 0xfa;
         diskMagic[1] = 0xbf;
         diskMagic[2] = 0xb5;

src/consensus/params.h

@@ -56,6 +56,8 @@ struct Params {
     int daaHeight;
     /** Unix time used for MTP activation of Nov 15 2018, hardfork */
     int magneticAnomalyActivationTime;
+    /** Unix time used for MTP activation of 15 May 2019 12:00:00 UTC upgrade */
+    int greatWallActivationTime;
     /**
      * Minimum blocks including miner confirmation of the total of 2016 blocks
      * in a retargeting period, (nPowTargetTimespan / nPowTargetSpacing) which

src/validation.cpp

@@ -600,12 +600,16 @@ static bool IsMagneticAnomalyEnabledForCurrentBlock(const Config &config) {
     return IsMagneticAnomalyEnabled(config, chainActive.Tip());
 }
 
+// Command-line argument "-replayprotectionactivationtime=<timestamp>" will
+// cause the node to switch to replay protected SigHash ForkID value when the
+// median timestamp of the previous 11 blocks is greater than or equal to
+// <timestamp>. Defaults to the pre-defined timestamp when not set.
 static bool IsReplayProtectionEnabled(const Config &config,
                                       int64_t nMedianTimePast) {
     return nMedianTimePast >= gArgs.GetArg("-replayprotectionactivationtime",
                                            config.GetChainParams()
                                                .GetConsensus()
-                                               .magneticAnomalyActivationTime);
+                                               .greatWallActivationTime);
 }
 
 static bool IsReplayProtectionEnabled(const Config &config,