s3: OneFS implementation of change notify

s3: OneFS implementation of change notify

The OneFS Samba implementation of change notify is modeled after the
usage of Linux's inotify kernel subsystem.  A single call is made
into the onefs.so VFS module to initialize kernel tracking of certain
file change events.  When these events occur a kernel notification is
sent to smbd and the notification event is translated and given to the
general Samba Change Notify layer through a callback function.

The most difficult aspect is converting an SMB CompletionFilter to
a matching ifs_event mask, and then back to an appropriate change
notify action.  Currently, not all possible cases are handled by the
this module, but the most prevalent ones, which are tested by
smbtorture, are implemented.