This commit reverts the following commits:
983fa68 darwin: fix 10.6 build error in fsevents.c
684e212 fsevents: use shared FSEventStream
ea4cb77 fsevents: FSEvents is most likely not thread-safe
9bae606 darwin: create fsevents thread on demand
Several people have reported stability issues on OS X 10.8 and bus
errors on the 10.9 developer preview.
See also joyent/node#6296 and joyent/node#6251.