Add WordPress.com OAuth2 plugin

Summary:
This plugin provides an OAuth authentication provider to authenticate users using WordPress.com Connect.

This diff corresponds to the github pull request: https://github.com/facebook/libphutil/pull/36

Test Plan: No test plan, at the moment.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D9004
Minor, update map.
Use the `ArcanistConfigurationDrivenLintEngine` as a linting engine.

Summary: Ref T2039. This diff is the equivalent to D9057, but for rPHU.

Test Plan: Ran `arc lint` and ensure it doesn't complain about the `.arclint` file.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T2039

Differential Revision: https://secure.phabricator.com/D9063
Add phutil-library linter to libphutil

Summary: Ref T2039. See D9070. D9072 is similar.

Test Plan: Ran `arc lint`.

Reviewers: btrahan, joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Maniphest Tasks: T2039

Differential Revision: https://secure.phabricator.com/D9074
Attempt to automatically build XHPAST.

Summary: Fixes T4951. Whilst `xhpast` was originally intended to be an internal development tool, it is not unreasonable for `ArcanistXHPASTLinter` to be used externally. Currently, however, if the compiled version of `xhpast` is not up-to-date, we simply exit and ask the user to build XHPAST themselves. Instead, let's try to build XHPAST automatically.

Test Plan: Removed `./src/parser/xhpast/bin/xhpast` and ran `arc lint` over a PHP file. Verified that the `xhpast` binary was created during this process.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T4951

Differential Revision: https://secure.phabricator.com/D9076