kqueue: split off newCreateEvent

more clear.
kqueue: pathInfo struct containing name and isDir

we don't use fileInfo for anything but IsDir
kqueue: don't return interrupted system call error

regression from my recent changes
FIXME: something doesn't seem quite right

Ref: https://github.com/go-fsnotify/fsnotify/blob/v0.9.0/fsnotify_bsd.go#L384
kqueue: less mutexes

closes #13