@filiphanes requested support for bytearray
and memoryview in the request body here:
<https://github.com/nginx/unit/issues/648>

This patch implements bytearray body support only.
Memoryview body still need to be implemented.

This commit introduces the 'vars' JavaScript object to NJS,
enabling direct access to native variables such as $uri and $arg_foo.
The syntax is `${vars.var_name}` or `${'vars[var_name]'}`.

For example:
    {
        "action": {
            "share": "`/www/html${vars.uri}`"
        }
    }

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

* Take options as well as requestListener

Unit-http have not kept up with the signature of nodejs's http package
development. Nodejs allows an optional `options` object to be passed to
the `createServer` function, we didn't. This resulted in function
signature errors when user code that did make use of the options arg
tried to call unit's replaced function.

This change changes the signature to be more in line with how nodejs
does it discarding it and printing a message to stdout.

* Add test file to start node application with options

* Add changes to docs/changes.xml

Closes: https://github.com/nginx/unit/issues/1043