Update `.gitignore`.

Summary: See inline comments for reasoning.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9528
Fix `ArcanistLesscLinter::getVersion` function.

Summary:
This `ArcanistLesscLinter::getCacheVersion` should have been renamed to `getVersion` as of D8971, but wasn't updated.

Also fix the regex to properly capture version information.

Test Plan: It's pretty difficult to test this stuff.... I have an idea that I will submit a separate diff for.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9475
Restore PEP8 errors.

Summary: As per the TODO comment, now that `.arclint` is more mature, we should be able to restore PEP8 errors.

Test Plan: N/A

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9473
Add a unit test to check `src/__phutil_library_map__.php`.

Summary: See D9557. Add a unit test to ensure that `src/__phutil_library_map__.php` is up-to-date.

Test Plan: Ran `arc unit`.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9558
Made some additional methods final.

Summary: Just some minor tidying up. I don't think that these methods should ever be overridden in subclasses.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9569
Update `update_compat_info.php` to use PHP_CompatInfo version 3

Summary:
Fixes T5377. The current `scripts/update_compat_info.php` script works for PHP CompatInfo version 2, but doesn't work with the newer version 3.

There are a few breaking changes in version 3 that had to be addressed:

- PHP 5.3 is required. Whilst Arcanist is generally compatible with PHP 5.2, I don't think that having this dependency presents any real issues because it is purely a development tool that is rarely updated.
- [[https://getcomposer.org/ | Composer]] is used for packaging, which makes including the library slightly more complicated. Basically, I had to install `PHP_CompatInfo` globally with Composer (`composer global require "bartlett/php-compatinfo"` and then symlink `~/.composer/vendor` into `externals/includes`.

Test Plan: Compared the `resources/php_compat_info.json` file. There are a bunch of functions/classes that //were// in this file but are no longer, but I think that I've covered the most popular extensions.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5377

Differential Revision: https://secure.phabricator.com/D9568
Add constants and class methods to `php_compat_info.json`.

Summary: Allows the `ArcanistXHPASTLinter` to determine whether constants can be used, based on the target PHP version. Also added class methods to the compatibility information, although this isn't used yet (it is small anyway).

Test Plan: Created a test file that contained the `JSON_PRETTY_PRINT` constant. Verified that a linter error was raised.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9571
Merge branch 'master' of github.com:facebook/arcanist