Accessing the event slot should only be done from the owner thread, since the chunk index of the ChoppedVector could be updated at any time. Instead of a triggerAll field, this flag is now propagated through the underlying eventfd/socket pair.
This doesn't duplicate the definitions form `core.sys.linux.sys.eventfd` and will pickup any platform specifics for better portability.
Fixes https://github.com/vibe-d/eventcore/issues/102
Unfortunately the built-in assert GC allocates an exception, which means that if called directly or indirectly form a finalizer, the assertion will not become visible and instead an InvalidMemoryOperationError is thrown.
This implements a custom nogc_assert() function that directly prints the assertion message and uses abort() to end the process.
