Modernize code

Update to pthreads 5.0

Merge branch 'master' of github.com:pmmp/Snooze

Require pthreads ~3.2.0 || ^4.0

Change example code to remove circular dependency

this way is better anyway, since it requires less locks.

actions: update PHP versions

Fixed race conditions between ThreadedSleeper->notifCount and Sleeper…

…Notifier->notification, closes #1

this requires synchronizing with the ThreadedSleeper to ensure that the notification count change and notification flag on the notifier get updated atomically, eliminating any chance of a race occurring between the two operations.

PHP 8.0 (#26)

phpstan-strict-rules

travis: remove 7.4, pthreads doesn't support it yet