Upgrade from 1.13.5 to 1.13.6.

<ChangeLog>

*) 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.

</ChangeLog>