Introduce FSEvents support for directory watcher on mac

[paulmillr]

inotify is a great and fast library for watching file system changes on Linux. Though, it doesn't work on macs.

Mac OS X 10.5+ has built-in support of very similar technology, called FSEvents.

I propose to add its support to node.

[bnoordhuis]

We use kqueue on darwin, which is similar to inotify and more portable than fsevents. It's what the freebsd port uses, for example.

[paulmillr]

I believe this should be reopened because of #2062.

kqueue sucks: it doesn't provide filename on os x etc.

//cc @ricardobeat

[bnoordhuis]

kqueue sucks: it doesn't provide filename on os x etc.

Let's turn that around. FSEvents sucks: it doesn't let you watch individual files. A hybrid approach would be susceptible to race conditions.

kqueue vs. FSEvents has been discussed a couple of times. The current consensus is that the pro's don't outweigh the cons (and that all file event APIs suck). We may revisit it some time in the future.