fix(interpreter): correctly compare values from 'verifyEval'

This is an attempt to fix an issue described in se-builder/se-builder#163
which allows comparison of evaluated values.

Before:
```js
{
  "type": "verifyEval",
  "script": "return true;",
  "value": "true"
}
//=> Error: "true" does not match "true"
```

After:
```js
{
  "type": "verifyEval",
  "script": "return true;",
  "value": "true"
}
//=> true
```

Closes: se-builder/se-builder#163