This was broken in a93345ee8f52 (1.9.8).

This flag makes sub filter flush buffered data and optimizes allocation in copy
filter.

With main request buffered, it's possible, that a slice subrequest will send
output before it.  For example, while main request is waiting for aio read to
complete, a slice subrequest can start an aio operation as well.  The order
in which aio callbacks are called is undetermined.

Skip SSL_CTX_set_tlsext_servername_callback in case of renegotiation.
Do nothing in SNI callback as in this case it will be supplied with
request in c->data which isn't expected and doesn't work this way.

This was broken by b40af2fd1c16 (1.9.6) with OpenSSL master branch and LibreSSL.

Splits a request into subrequests, each providing a specific range of response.
The variable "$slice_range" must be used to set subrequest range and proper
cache key.  The directive "slice" sets slice size.

The following example splits requests into 1-megabyte cacheable subrequests.

server {
    listen 8000;

    location / {
        slice 1m;

        proxy_cache cache;
        proxy_cache_key $uri$is_args$args$slice_range;
        proxy_set_header Range $slice_range;
        proxy_cache_valid 200 206 1h;
        proxy_pass http://127.0.0.1:9000;
    }
}

The NGX_PTR_SIZE macro is only needed in preprocessor directives where
it's not possible to use sizeof().

This is an API change.

The proxy module was modified to not depend on this in 44122bddd9a1.
No known third-party modules seem to depend on this.

Do not assume that space character follows the method name, just pass it
explicitly.

The fuss around it has already proved to be unsafe, see bbdb172f0927 and
http://mailman.nginx.org/pipermail/nginx-ru/2013-January/049692.html for
details.