child_process: do not keep list of sent sockets

Keeping list of all sockets that were sent to child process causes memory
leak and thus unacceptable (see #4587). However `server.close()` should
still work properly.

This commit introduces two options:

* child.send(socket, { track: true }) - will send socket and track its status.
  You should use it when you want `server.connections` to be a reliable
  number, and receive `close` event on sent sockets.
* child.send(socket) - will send socket without tracking it status. This
  performs much better, because of smaller number of RTT between master and
  child.

With both of these options `server.close()` will wait for all sent
sockets to get closed.
benchmark: Add resume() in static_http_server
Revert "child_process: do not keep list of sent sockets"

This reverts commit db5ee0b3decace9b5d80ee535ce53183aff02909.
child_process: do not keep list of sent sockets

Keeping list of all sockets that were sent to child process causes memory
leak and thus unacceptable (see #4587). However `server.close()` should
still work properly.

This commit introduces two options:

* child.send(socket, { track: true }) - will send socket and track its status.
  You should use it when you want to receive `close` event on sent sockets.
* child.send(socket) - will send socket without tracking it status. This
  performs much better, because of smaller number of RTT between master and
  child.

With both of these options `server.close()` will wait for all sent
sockets to get closed.
v8: add %p option to --logfile, expands to pid

Useful when you are profiling multiple instances of V8 concurrently.
Submitted upstream: http://code.google.com/p/v8/issues/detail?id=2503

Refs #4617.