Poettering: Introducing sd-event

Lennart Poettering introduces thesd-event API for the implementation of event loops. "sd-event.h, ofcourse, is not the first event loop API around, and it doesn't implementany really novel concepts. When we started working on it we tried to do ourhomework, and checked the various existing event loop APIs, maybe lookingfor candidates to adopt instead of doing our own, and to learn about thestrengths and weaknesses of the various implementationsexisting. Ultimately, we found no implementation that could deliver what weneeded, or where it would be easy to add the missing bits: as usual in thesystemd project, we wanted something that allows us access to all theLinux-specific bits, instead of limiting itself to the least commondenominator of UNIX."