merge changes between nginx 1.4.4 and 1.4.5

Details are as following:

* Bugfix: the $ssl_session_id variable contained full session
  serialized instead of just a session id.
  Thanks to Ivan Ristić.
  
  Changeset: http://hg.nginx.org/nginx/rev/70f4d99ded41
  
* Bugfix: client connections might be immediately closed if deferred
  accept was used; the bug had appeared in 1.3.15.
  
  Changeset: http://hg.nginx.org/nginx/rev/462ae7eedc68
  
* Bugfix: alerts "zero size buf in output" might appear in logs while
  proxying; the bug had appeared in 1.3.9.
  
  Changeset:  http://hg.nginx.org/nginx/rev/3b7463b08747
  
* Bugfix: a segmentation fault might occur in a worker process if the
  ngx_http_spdy_module was used.
  
  Changeset: http://hg.nginx.org/nginx/rev/b8e6297358b5
  
* Bugfix: proxied WebSocket connections might hang right after
  handshake if the select, poll, or /dev/poll methods were used.
  
  Changeset: http://hg.nginx.org/nginx/rev/560de9681661
  
  More details are available here:
  http://mailman.nginx.org/pipermail/nginx/2014-January/041839.html
  
* Bugfix: a timeout might occur while reading client request body in an
  SSL connection using chunked transfer encoding.
  
  Changeset: http://hg.nginx.org/nginx/rev/35b00bcf72fe
  
  More details are available here:
  http://mailman.nginx.org/pipermail/nginx/2013-November/041178.html
  
* Bugfix: memory leak in nginx/Windows.
  
  Changeset: http://hg.nginx.org/nginx/rev/fd77e2018652
  
  **Note that this patch is not merged because tengine does not support win32.**