Add a test filter for RETURNDATACOPY initially copying zeros

; hex  description
;; store some non-zero word into memory [0..31]
30   ADDRESS
6000 PUSH1 [0]
52   MSTORE

;; RETURNDATACOPY should copy the first word into memory [0..31]
6020 PUSH1 [32]
6000 PUSH1 [0]
6000 PUSH1 [0]
0e   RETURNDATACOPY

;; load memory[0..31] onto stack
6000 PUSH1 [0]
51   MLOAD

;; store the topmost stack into storage [0]
6000 PUSH1 [0]
55   SSTORE

;; an implicit `STOP` follows.

Author: pirapira

src/GeneralStateTestsFiller/stReturnDataTest/returndatacopy_initial.json

@@ -0,0 +1,74 @@
+{
+    "returndatacopy_initial" : {
+        "env" : {
+            "currentCoinbase" : "0x2adc25665018aa1fe0e6bc666dac8fc2697ff9ba",
+            "currentDifficulty" : "0x20000",
+            "currentGasLimit" : "0x0a00000000",
+            "currentNumber" : "0x01",
+            "currentTimestamp" : "0x03e8",
+            "previousHash" : "0x5e20a0453cecd065ea59c37ac63e079ee08998b6045136a8ce6635c7912ec0b6"
+        },
+        "expect" : [
+            {   "indexes" : {
+                   "data" : -1,
+                   "gas" : -1,
+                   "value" : -1
+                },
+                "network" : ["EIP150", "EIP158", "Frontier", "Homestead"],
+                "result" : {
+                    "0x0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6" : {
+                        "storage" : {
+                            "0x00" : "0x01"
+                        }
+                    }
+                }
+            },
+            {   "indexes" : {
+                   "data" : -1,
+                   "gas" : -1,
+                   "value" : -1
+                },
+                "network" : ["Metropolis"],
+                "result" : {
+                    "0x0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6" : {
+                        "storage" : {
+                            "0x00" : "0x00"
+                        }
+                    }
+                }
+            }
+        ],
+        "pre" : {
+            "0x0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6" : {
+                "balance" : "0x0de0b6b3a7640000",
+                "code" : "0x306000526020600060000e600051600055",
+                "nonce" : "0x00",
+                "storage" : {
+                    "0x00" : "0x01"
+                }
+            },
+            "0xa94f5374fce5edbc8e2a8697c15331677e6ebf0b" : {
+                "balance" : "0x6400000000",
+                "code" : "",
+                "nonce" : "0x00",
+                "storage" : {
+                }
+            }
+        },
+        "transaction" : {
+            "data" : [
+                ""
+            ],
+            "gasLimit" : [
+                "0x0a00000000"
+            ],
+            "gasPrice" : "0x01",
+            "nonce" : "0x00",
+            "secretKey" : "0x45a915e4d060149eb4365960e6a7a45f334393093061116b197e3240065ff2d8",
+            "to" : "0x0f572e5295c57f15886f9b263e2f6d2d6c7b5ec6",
+            "value" : [
+                "0x00"
+            ]
+        }
+    }
+}