Auto merge of #2227 - str4d:2074-ignore-virtual-cores, r=str4d

Use real number of cores, ignore virtual cores

Cherry-picked from the following upstream PRs:

- bitcoin/bitcoin#6361
- bitcoin/bitcoin#6370

Part of #2074.

src/chainparams.cpp

@@ -59,7 +59,6 @@ public:
         pchMessageStart[3] = 0x64;
         vAlertPubKey = ParseHex("04b7ecf0baa90495ceb4e4090f6b2fd37eec1e9c85fac68a487f3ce11589692e4a317479316ee814e066638e1db54e37a10689b70286e6315b1087b6615d179264");
         nDefaultPort = 8233;
-        nMinerThreads = 0;
         nMaxTipAge = 24 * 60 * 60;
         nPruneAfterHeight = 100000;
         const size_t N = 200, K = 9;
@@ -219,7 +218,6 @@ public:
         pchMessageStart[3] = 0xbf;
         vAlertPubKey = ParseHex("044e7a1553392325c871c5ace5d6ad73501c66f4c185d6b0453cf45dec5a1322e705c672ac1a27ef7cdaf588c10effdf50ed5f95f85f2f54a5f6159fca394ed0c6");
         nDefaultPort = 18233;
-        nMinerThreads = 0;
         nPruneAfterHeight = 1000;
 
         //! Modify the testnet genesis block so the timestamp is valid for a later start.
@@ -308,7 +306,6 @@ public:
         pchMessageStart[1] = 0xe8;
         pchMessageStart[2] = 0x3f;
         pchMessageStart[3] = 0x5f;
-        nMinerThreads = 1;
         nMaxTipAge = 24 * 60 * 60;
         const size_t N = 48, K = 5;
         BOOST_STATIC_ASSERT(equihash_parameters_acceptable(N, K));