The copyright and license notice is already in the LICENSE file. There is no justifiable reason to also require that it be included in every file, since the individual files are not individually distributed except as part of the entire package.
async, timer, prepare, idle and check handles no longer get a status parameter since they can never fail.
fix #6899
This implements a nested event loop that makes it possible to control a child process, while blocking the main loop until the process exits.