v1.2.1: Bugfixes and minor improvements

This version fixes a bug which triggered when an event loop was constructed with delayed initialisation and then never initialised before being destroyed. On systems using POSIX timers (such as FreeBSD), this could cause a crash.

On Linux, eventfd is used as the mechanism to signal an event loop in another thread, rather than a pipe. This uses one less file descriptor and is more efficient generally.

Some minor packaging issues have been resolved.