ts-node: issue listening to SIGINT using child processes

Whilst issue 457 has been fixed on version 4.1.x of ts-node, when using child processes, ts-node is still miss-behaving.

I'm using the cluster module, and listening for the SIGINT signal on the master and child processes.

ts-node behaviour:

SIGINT can be catched only for the master process.

$ ./node_modules/.bin/ts-node index.ts
^CShutting down MASTER...
MASTER has been shut down.

node behaviour:

SIGINT can be catched for master and child process.

$ node index.js
^CShutting down CHILD...
Shutting down MASTER...
CHILD has been shut down.
MASTER has been shut down.