Do not depend on deprecated 'constants' module

[kt3k]

constants module has been deprecated since v6.3.0 (ref: https://nodejs.org/api/deprecations.html#DEP0008 ). This PR updates the use of constants to fs.constants.

BTW fs.constants doesn't inherit from Object.prototype (ref: nodejs/node#10458 ), so I updated constants.hasOwnProperty('O_SYMLINK') to constants.O_SYMLINK !== undefined. (This change was discussed in node.js repository nodejs/node#10458 (comment) )

[aminya]

This is causing a lot of issues for me. @isaacs Please take a look

[aminya]

fs-extra is broken and cannot be bundled because of this.

[anthonyborell]

@isaacs Would be great if you could take a look at this. As per https://nodejs.org/api/deprecations.html#DEP0008

The constants module is deprecated. When requiring access to constants relevant to specific Node.js builtin modules, developers should instead refer to the constants property exposed by the relevant module. For instance, require('fs').constants and require('os').constants.