Added new connection states CONN_STATE_HANDLER and CONN_STATE_WRITE_COMPLETION.

Also, core_create_conn() now initializes the conn_state within the newly
created connection.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/async-dev@280221 13f79535-47bb-0310-9956-ffa450edef68