core/vm: removed own concoction of a mem dumper

Replaced custom implementation of memory dumper with hex.Dump which
outputs exact same information as hexdump -C.

cmd/easm/examples/string.asm

@@ -1 +1,3 @@
 	push "hello"
+	push 0
+	mstore

core/vm/logger.go

@@ -17,10 +17,10 @@
 package vm
 
 import (
+	"encoding/hex"
 	"fmt"
 	"math/big"
 	"os"
-	"unicode"
 
 	"github.com/ethereum/go-ethereum/common"
 )
@@ -183,24 +183,8 @@ func StdErrFormat(logs []StructLog) {
 			fmt.Fprintf(os.Stderr, "%04d: %x\n", len(log.Stack)-i-1, common.LeftPadBytes(log.Stack[i].Bytes(), 32))
 		}
 
-		const maxMem = 10
-		addr := 0
 		fmt.Fprintln(os.Stderr, "MEM =", len(log.Memory))
-		for i := 0; i+16 <= len(log.Memory) && addr < maxMem; i += 16 {
-			data := log.Memory[i : i+16]
-			str := fmt.Sprintf("%04d: % x  ", addr*16, data)
-			for _, r := range data {
-				if r == 0 {
-					str += "."
-				} else if unicode.IsPrint(rune(r)) {
-					str += fmt.Sprintf("%s", string(r))
-				} else {
-					str += "?"
-				}
-			}
-			addr++
-			fmt.Fprintln(os.Stderr, str)
-		}
+		fmt.Fprintln(os.Stderr, hex.Dump(log.Memory))
 
 		fmt.Fprintln(os.Stderr, "STORAGE =", len(log.Storage))
 		for h, item := range log.Storage {