process.kill(pid, signal) does not recognize common signal strings

I am getting this error:

```
 Uncaught exception: TypeError [ERR_UNKNOWN_SIGNAL]: Unknown signal: INT
```

and it was used like:

```js
    process.kill(num, 'INT');
```

this works tho:

```js
    process.kill(num, 'SIGINT');
```

it should probably work with the short signal names?
