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(bug fix release, release 2010-08-30)
* check max_content_length negative
* add set_backlog (default 8192)
* add set_picoev_max_fd (default 8192)
* support keep-alive timeout (use set_keepalive method, set timeout value)
* fix websocket closed bug
* enable --keep-alive and --worker-connections option
* various bug fixes