Update to 0.23

Upstream changes:
0.23  2013-01-26

- The new_events() watcher method blocked when using IO::Kqueue as the watcher
  backend. Reported and patched by Jun Kuriyama.

0.22  2012-04-13

- Remove unnecessary Perl 5.10 requirement.

0.21  2012-02-03

- The implementation of the exclude feature did not work properly in several
  cases. First, for the Inotify and KQueue watchers, when a new directory was
  created that should have been excluded, it was not. Second, it didn't work
  for files at all for these watchers. Reported by Jon Swartz. RT #73089.

(wen)