kqueue: less mutexes
kqueue: less mutexes

closes #13

qida/fsnotify,fsnotify/fsnotify,beni55/fsnotify,jsix/fsnotify,fsnotify/fsnotify,mingshun/fsnotify,scalingdata/fsnotify-v1,omeid/fsnotify,treejames/fsnotify,fsnotify/fsnotify