tevent: change version to 0.9.18

tevent: change version to 0.9.18

This release contains a lot of fixes:

- Adding new timer events is now faster, if there's
  a large number of timer events.

- sigprocmask does not work on FreeBSD to stop further signals in a signal
  handler.

- TEVENT_NUM_SIGNALS is calculated by configure in order
  to support realtime signals on freebsd.

- ./configure --disable-python was fixed for the standalone build.

- Several crash bugs in the poll backend are fixed.

- The poll backend removes deleted events from the
  cached pollfd array now.

- The poll doesn't pass pollfd.events == 0 to poll()
  and maintains a list of disabled events,
  instead of consuming 100% cpu and/or triggering
  the callers handler.

- The poll backend detects POLLNVAL and reports EBADF
  instead of consuming 100% cpu.

- The select backend supports separate handlers
  for TEVENT_FD_READ and TEVENT_FD_WRITE.

- The poll and select backends are now doing fair
  queuing of fd events.

- The epoll has better error checking
  and supports separate handlers
  for TEVENT_FD_READ and TEVENT_FD_WRITE.

- The standard backend was rewritten to be a tiny
  wrapper on top of epoll with a fallback to poll,
  which means that it doesn't use select directly anymore.

- TEVENT_TRACE_BEFORE_LOOP_ONCE and TEVENT_TRACE_AFTER_LOOP_ONCE
  are added in order to allow the application to hook in
  before and after the loop_once() backend function is called.
  The TEVENT_HAS_LOOP_ONCE_TRACE_POINTS define can be used to
  detect the new feature.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sat Mar  2 02:15:44 CET 2013 on sn-devel-104