Auto merge of #3263 - str4d:ibd-upstream-changes, r=bitcartel

InitialBlockDownload upstream changes

Cherry-picked from the following upstream PRs:

- bitcoin/bitcoin#7208
- bitcoin/bitcoin#8007
- bitcoin/bitcoin#9053
  - Excluding second commit (requires bitcoin/bitcoin#8865)
- bitcoin/bitcoin#10388

src/chainparams.cpp

@@ -106,6 +106,9 @@ public:
         consensus.vUpgrades[Consensus::UPGRADE_SAPLING].nActivationHeight =
             Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT;
 
+        // The best chain should have at least this much work.
+        consensus.nMinimumChainWork = uint256S("0x00000000000000000000000000000000000000000000000000281b32ff3198a1");
+
         /**
          * The message start string should be awesome! ⓩ❤
          */
@@ -115,7 +118,6 @@ public:
         pchMessageStart[3] = 0x64;
         vAlertPubKey = ParseHex("04b7ecf0baa90495ceb4e4090f6b2fd37eec1e9c85fac68a487f3ce11589692e4a317479316ee814e066638e1db54e37a10689b70286e6315b1087b6615d179264");
         nDefaultPort = 8233;
-        nMaxTipAge = 24 * 60 * 60;
         nPruneAfterHeight = 100000;
         const size_t N = 200, K = 9;
         BOOST_STATIC_ASSERT(equihash_parameters_acceptable(N, K));
@@ -273,13 +275,15 @@ public:
         consensus.vUpgrades[Consensus::UPGRADE_SAPLING].nProtocolVersion = 170006;
         consensus.vUpgrades[Consensus::UPGRADE_SAPLING].nActivationHeight = 252500;
 
+        // The best chain should have at least this much work.
+        consensus.nMinimumChainWork = uint256S("0x00000000000000000000000000000000000000000000000000000001d0c4d9cd");
+
         pchMessageStart[0] = 0xfa;
         pchMessageStart[1] = 0x1a;
         pchMessageStart[2] = 0xf9;
         pchMessageStart[3] = 0xbf;
         vAlertPubKey = ParseHex("044e7a1553392325c871c5ace5d6ad73501c66f4c185d6b0453cf45dec5a1322e705c672ac1a27ef7cdaf588c10effdf50ed5f95f85f2f54a5f6159fca394ed0c6");
         nDefaultPort = 18233;
-        nMaxTipAge = 24 * 60 * 60;
         nPruneAfterHeight = 1000;
         const size_t N = 200, K = 9;
         BOOST_STATIC_ASSERT(equihash_parameters_acceptable(N, K));
@@ -328,6 +332,7 @@ public:
         fMineBlocksOnDemand = false;
         fTestnetToBeDeprecatedFieldRPC = true;
 
+
         checkpointData = (CCheckpointData) {
             boost::assign::map_list_of
             (0, consensus.hashGenesisBlock)
@@ -391,12 +396,14 @@ public:
         consensus.vUpgrades[Consensus::UPGRADE_SAPLING].nActivationHeight =
             Consensus::NetworkUpgrade::NO_ACTIVATION_HEIGHT;
 
+        // The best chain should have at least this much work.
+        consensus.nMinimumChainWork = uint256S("0x00");
+
         pchMessageStart[0] = 0xaa;
         pchMessageStart[1] = 0xe8;
         pchMessageStart[2] = 0x3f;
         pchMessageStart[3] = 0x5f;
         nDefaultPort = 18344;
-        nMaxTipAge = 24 * 60 * 60;
         nPruneAfterHeight = 1000;
         const size_t N = 48, K = 5;
         BOOST_STATIC_ASSERT(equihash_parameters_acceptable(N, K));