Changes for version 1.3
- stopping idle/check/prepare watchers could cause data corruption.
- implement and document EV::once.
- improved documentation, verify that netbsd indeed has the only working kqueue implementation (out of darwin, freebsd, netbsd and openbsd). Praise them!
- fix the data method so it might work.
- expose ev_ref/ev_unref to the C API.
- expose ref/unref in form of the ->keepalive method to perl.
- minor bugfixes and portability fixes.