r14877: added support for the kernel inotify mechanism. This passes basic

r14877: added support for the kernel inotify mechanism. This passes basic
tests, but still needs some more work to ensure we correctly cope with
events that may generate both a system inotify event and a internal
notify event. The system inotify events won't handle recursion, and
don't understand things like streams.

This also adds the ntvfs/sysdep/ directory, which is meant for system
dependent code that is not tied to a particular ntvfs backend. The
inotify code is a good example of that.
(This used to be commit eadadbb44adb3c4081d6ff1d85a9b850a0227059)