M1 support

A complete rework, now with support for M1 silicon.

Single sleep

This is a major update that includes a fix for a nasty long-lasting issue when the script was telling macOS to go to sleep when it was sleeping already and awoke for a second to check something.

1.1: External semaphore to only invoke `sleepnow` once

It still fails to wake up time to time, even on latest MacOS, with all the tricks.
I have no idea how to debug that.

Initial version

Works like a charm. Nothing else to say.