Update nginx from 1.17.7 to 1.17.8.
Update third-party njs module from 0.3.7 to 0.3.8.

<ChangeLog with nginx 1.17.8>

*) Feature: variables support in the "grpc_pass" directive.

*) Bugfix: a timeout might occur while handling pipelined requests in an

SSL connection; the bug had appeared in 1.17.5.

*) Bugfix: in the "debug_points" directive when using HTTP/2.

Thanks to Daniil Bondarev.

</ChangeLog>

<ChangeLog with njs 0.3.8>

nginx modules:

*) Feature: added Promise support for r.subrequest(). If callback

is not provided r.subrequest() returns an ordinary Promise object
that resolves to subrequest response object.

*) Change: r.parent property handler now returns "undefined"

instead of throwing exception if parent object is not available.

Core:

*) Feature: added Promise support. Implemented according to

the specification without: Promise.all(), Promise.allSettled(),
Promise.race().

*) Feature: added initial Typed-arrays support.

Thanks to Tiago Natel de Moura.

*) Feature: added ArrayBuffer support.

Thanks to Tiago Natel de Moura.

*) Feature: added initial Symbol support.

Thanks to Artem S. Povalyukhin.

*) Feature: added externals supopor for JSON.stringify().

*) Feature: added Object.is().

Thanks to Artem S. Povalyukhin.

*) Feature: added Object.setPrototypeOf().

Thanks to Artem S. Povalyukhin.

*) Feature: introduced nullish coalescing operator.

Thanks to Valentin Bartenev.

*) Bugfix: fixed Object.getPrototypeOf() according to the

specification.

*) Bugfix: fixed Object.prototype.valueOf() according to the

specification.

*) Bugfix: fixed JSON.stringify() with unprintable values and

replacer function.

*) Bugfix: fixed operator "in" according to the specification.

*) Bugfix: fixed Object.defineProperties() according to the

specification.

*) Bugfix: fixed Object.create() according to the specification.

Thanks to Artem S. Povalyukhin.

*) Bugfix: fixed Number.prototype.toString(radix) when

fast-math is enabled.

*) Bugfix: fixed RegExp() instance properties.

*) Bugfix: fixed import segfault.

Thanks to 洪志道 (Hong Zhi Dao).

</ChangeLog>