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 workaround from baf2816d556d stopped to work because the order of
"-arch x86_64" and "-arch i386" has changed.

It is more effective, because it doesn't require a separate lseek().

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

The SPDY support is removed, as it's incompatible with the new module.

stream {
    limit_conn_zone $binary_remote_addr zone=perip:1m;
    limit_conn_log_level error;

    server {
        ...
        limit_conn perip 1;
    }
}

Signed-off-by: Piotr Sikora <piotr@cloudflare.com>

Based on a patch by Piotr Sikora.