core, core/vm, tests: changed the initialisation behaviour of the EVM

The EVM was previously initialised and created for every CALL, CALLCODE,
DELEGATECALL and CREATE. This PR changes this behaviour so that the same
EVM can be used through the session and beyond as long as the
Environment sticks around.

core/vm/vm.go

@@ -30,15 +30,12 @@ import (
 
 // Vm is an EVM and implements VirtualMachine
 type Vm struct {
-	env Environment
+	env       Environment
+	jumpTable vmJumpTable
 }
 
-// New returns a new Vm
-func New(env Environment) *Vm {
-	// init the jump table. Also prepares the homestead changes
-	jumpTable.init(env.BlockNumber())
-
-	return &Vm{env: env}
+func EVM(env Environment) *Vm {
+	return &Vm{env: env, jumpTable: newJumpTable(env.BlockNumber())}
 }
 
 // Run loops and evaluates the contract's code with the given input data
@@ -169,7 +166,7 @@ func (self *Vm) Run(contract *Contract, input []byte) (ret []byte, err error) {
 		mem.Resize(newMemSize.Uint64())
 		// Add a log message
 		self.log(pc, op, contract.Gas, cost, mem, stack, contract, nil)
-		if opPtr := jumpTable[op]; opPtr.valid {
+		if opPtr := self.jumpTable[op]; opPtr.valid {
 			if opPtr.fn != nil {
 				opPtr.fn(instruction{}, &pc, self.env, contract, mem, stack)
 			} else {