ITS#2482 slapd out of fd's

["Howard Chu" <hyc@highlandsun.com>]

I think a better approach might be to remove all the listeners from the
readfds fdset when we get an EMFILE error and don't replace them until at
least one other socket closes. We should probably also use a timeval on the
select() to implement connection timeouts instead of the current approach,
because the current code won't timeout any connection until select() returns
due to activity on some other connection.

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support