due to a subtle HFS+ filesystem corruption bug in OSX, the kernel may be
reporting events using a different case than what the fsevents daemon is
expecting. to work around this, we have to override the behavior of realpath()
before calling FSEventStreamCreate() to force fsevents to use the expected
case. note that we're detecting whether or not the hack is required before
overriding realpath(), so most of the time behavior should be the same.