params: core, core/vm, miner: 64bit gas instructions (#3514)

Reworked the EVM gas instructions to use 64bit integers rather than
arbitrary size big ints. All gas operations, be it additions,
multiplications or divisions, are checked and guarded against 64 bit
integer overflows.

In additon, most of the protocol paramaters in the params package have
been converted to uint64 and are now constants rather than variables.

* common/math: added overflow check ops
* core: vmenv, env renamed to evm
* eth, internal/ethapi, les: unmetered eth_call and cancel methods
* core/vm: implemented big.Int pool for evm instructions
* core/vm: unexported intPool methods & verification methods
* core/vm: added memoryGasCost overflow check and test

core/vm/jump_table.go

@@ -17,6 +17,7 @@
 package vm
 
 import (
+	"errors"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/params"
@@ -24,11 +25,13 @@ import (
 
 type (
 	executionFunc       func(pc *uint64, env *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error)
-	gasFunc             func(params.GasTable, *EVM, *Contract, *Stack, *Memory, *big.Int) *big.Int
+	gasFunc             func(params.GasTable, *EVM, *Contract, *Stack, *Memory, uint64) (uint64, error) // last parameter is the requested memory size as a uint64
 	stackValidationFunc func(*Stack) error
 	memorySizeFunc      func(*Stack) *big.Int
 )
 
+var errGasUintOverflow = errors.New("gas uint64 overflow")
+
 type operation struct {
 	// op is the operation function
 	execute executionFunc
@@ -431,7 +434,7 @@ func NewJumpTable() [256]operation {
 		},
 		STOP: {
 			execute:       opStop,
-			gasCost:       constGasFunc(Zero),
+			gasCost:       constGasFunc(0),
 			validateStack: makeStackFunc(0, 0),
 			halts:         true,
 			valid:         true,