Add EIP-2200 gas parameters for Istanbul

src/hardforks/istanbul.json

@@ -30,6 +30,38 @@
     "txDataNonZero": {
       "v": 16,
       "d": "Per byte of data attached to a transaction that is not equal to zero. NOTE: Not payable on data of calls between transactions"
+    },
+    "sstoreSentryGasEIP2200": {
+      "v": 2300,
+      "d": "Minimum gas required to be present for an SSTORE call, not consumed"
+    },
+    "sstoreNoopGasEIP2200": {
+      "v": 800,
+      "d": "Once per SSTORE operation if the value doesn't change"
+    },
+    "sstoreDirtyGasEIP2200": {
+      "v": 800,
+      "d": "Once per SSTORE operation if a dirty value is changed"
+    },
+    "sstoreInitGasEIP2200": {
+      "v": 20000,
+      "d": "Once per SSTORE operation from clean zero to non-zero"
+    },
+    "sstoreInitRefundEIP2200": {
+      "v": 19200,
+      "d": "Once per SSTORE operation for resetting to the original zero value"
+    },
+    "sstoreCleanGasEIP2200": {
+      "v": 5000,
+      "d": "Once per SSTORE operation from clean non-zero to something else"
+    },
+    "sstoreCleanRefundEIP2200": {
+      "v": 4200,
+      "d": "Once per SSTORE operation for resetting to the original non-zero value"
+    },
+    "sstoreClearRefundEIP2200": {
+      "v": 15000,
+      "d": "Once per SSTORE operation for clearing an originally existing storage slot"
     }
   },
   "vm": {},