[ticket/12825] Better sniff for the extensions and skip the vendor/ directory

PHPBB3-12825
Merge pull request #2706 from Nicofuma/ticket/12825

[ticket/12825] Better sniff for the extensions and skip the vendor/ directory

* Nicofuma/ticket/12825:
  [ticket/12825] Better sniff for the extensions and skip the vendor/ directory
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12825] Better sniff for the extensions and skip the vendor/ directory