www/nginx-devel: update NGINX JavaScript module to 0.6.0.

Bump PORTREVISION.

<ChangeLog for njs 0.5.3>

Core:

*) Feature: added let and const declaration support.

*) Feature: added RegExp.prototype[Symbol.split].

*) Feature: added sticky flag support for RegExp.

*) Bugfix: fixed heap-buffer-overflow in

String.prototype.lastIndexOf().

*) Bugfix: fixed RegExp.prototype.test() according to the

specification.

*) Bugfix: fixed String.prototype.split() according to the

specification.

*) Bugfix: fixed use-of-uninitialized-value while tracking

rejected promises.

*) Bugfix: fixed njs.dump() for objects with circular

references.

</ChangeLog>