Update from 1.15.11 to 1.15.12.
Update third-party njs module from 0.3.0 to 0.3.1.

<ChangeLogs>

Changes with nginx 1.15.12 16 Apr 2019

*) Bugfix: a segmentation fault might occur in a worker process if

variables were used in the "ssl_certificate" or "ssl_certificate_key"
directives and OCSP stapling was enabled.

Changes with njs 0.3.1 16 Apr 2019

Core:

*) Feature: added arrow functions support.

Thanks to 洪志道 (Hong Zhi Dao) and Artem S. Povalyukhin.

*) Feature: added Added Object.getOwnPropertyNames().

Thanks to Artem S. Povalyukhin.

*) Feature: added Added Object.getOwnPropertyDescriptors().

Thanks to Artem S. Povalyukhin.

*) Feature: making proto accessor descriptor of Object instances

mutable.

*) Feature: added shebang support in CLI.

*) Feature: added support for module mode execution in CLI. In module

mode global this is unavailable.

*) Bugfix: fixed editline detection.

*) Bugfix: fixed Function.prototype.bind().

Thanks to 洪志道 (Hong Zhi Dao).

*) Bugfix: fixed checking of duplication of parameters for functions.

Thanks to 洪志道 (Hong Zhi Dao).

*) Bugfix: fixed function declaration with the same name as a variable.

Thanks to 洪志道 (Hong Zhi Dao).

*) Improvement: code related to parsing of objects, variables and

functions is refactored.
Thanks to 洪志道 (Hong Zhi Dao).

*) Improvement: console.log() improved for outputting large values.

*) Improvement: console.log() improved for outputting strings in a

compliant way (without escaping and quotes).

*) Improvement: using ES6 version of ToInt32(), ToUint32(), ToLength().

</ChangeLogs>