r3507: - added deferred replies on sharing violation in pvfs open. The

r3507: - added deferred replies on sharing violation in pvfs open. The
  deferred reply is short-circuited immediately when the file is
  closed by another user, allowing it to be opened by the waiting user.

- added a sane set of timeval manipulation routines

- converted all the events code and code that uses it to use struct
  timeval instead of time_t, which allows for microsecond resolution
  instead of 1 second resolution. This was needed for doing the pvfs
  deferred open code, and is why the patch is so big.
(This used to be commit 0d51511d408d91eb5f68a35e980e0875299b1831)