Non-literal global constants

There are a few cases where we need to define a constant that its value is dependent on another constant.

```
const SCRIPT_INPUT0_SIZE = 32;
const SCRIPT_INPUTS_SIZE = 1 + SCRIPT_INPUT0_SIZE; // OP_PUSHDATA1 SCRIPT_INPUT0
...
    require(tx.inputs[0].lockingBytecode.split(SCRIPTINPUTS_SIZE)[0] +
                 A_NEW_BYTECODE == tx.outputs[0].lockingBytecode);
...
```