[Anizoptera] LibEvent component (complex commit): - MINOR: More complex examples - IMPROVED: Better support for fork in the newest libevent versions - FEATURE: Full fork control with `EventBase::fork()` - FEATURE: Event loops manager moved from `CliBase` and improved - FEATURE: Reentrant loop invocation protection (needed for the newest libevent versions) - IMPROVED: Tests added
Merge changes to AzaLibEvent subtree