[ticket/13120] Follows the symlinks in phpbb_load_extensions_autoloaders

PHPBB3-13120
Merge pull request #3010 from Nicofuma/ticket/13120

[ticket/13120] Follows the symlinks in phpbb_load_extensions_autoloaders

* Nicofuma/ticket/13120:
  [ticket/13120] Follows the symlinks in phpbb_load_extensions_autoloaders