Wiki updated with reset_timedout_connection.

[locojohn]

This directive enables or disables resetting the connection upon
timeout.  When resetting the connection, before the socket is closed,
the SO_LINGER option is set to the socket with timeout value of 0, which
forces RST packet to be sent to client upon closing the socket, while
all memory associated with the socket is freed.  This allows to avoid
the situation when the already closed socket is in the FIN_WAIT1 state
with the loaded buffers. 

The keepalive connections, after timeout, are closed in the usual way.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,212456,212460#msg-212460