Update from 1.5.2 to 1.5.3.
Temporary ignore following third-party modules support:
*) Change in internal API: now u->length defaults to -1 if working with
backends in unbuffered mode.
*) Change: now after receiving an incomplete response from a backend
server nginx tries to send an available part of the response to a
client, and then closes client connection.
*) Bugfix: a segmentation fault might occur in a worker process if the
ngx_http_spdy_module was used with the "client_body_in_file_only"
*) Bugfix: the "so_keepalive" parameter of the "listen" directive might
be handled incorrectly on DragonFlyBSD.
Thanks to Sepherosa Ziehau.
*) Bugfix: in the ngx_http_xslt_filter_module.
*) Bugfix: in the ngx_http_sub_filter_module.