nginx 1.13.6 fix

Changes with nginx 1.13.6 10 Oct 2017

*) Bugfix: switching to the next upstream server in the stream module
did not work when using the "ssl_preread" directive.

*) Bugfix: in the ngx_http_v2_module.
Thanks to Piotr Sikora.

*) Bugfix: nginx did not support dates after the year 2038 on 32-bit
platforms with 64-bit time_t.

*) Bugfix: in handling of dates prior to the year 1970 and after the
year 10000.

*) Bugfix: in the stream module timeouts waiting for UDP datagrams from
upstream servers were not logged or logged at the "info" level
instead of "error".

*) Bugfix: when using HTTP/2 nginx might return the 400 response without
logging the reason.

*) Bugfix: in processing of corrupted cache files.

*) Bugfix: cache control headers were ignored when caching errors
intercepted by error_page.

*) Bugfix: when using HTTP/2 client request body might be corrupted.

*) Bugfix: in handling of client addresses when using unix domain
sockets.

*) Bugfix: nginx hogged CPU when using the "hash ... consistent"
directive in the upstream block if large weights were used and all or
most of the servers were unavailable.