It seems these files in the same folder also needs changing:
./phpbb_captcha_qa_plugin.php:104: $instance =& new
phpbb_captcha_qa();
./phpbb_recaptcha_plugin.php:59:$instance =& new
phpbb_recaptcha();
./phpbb_captcha_nogd_plugin.php:45: $instance =& new
Public bug reported:
Relevant installed packages:
phpbb3/xenial,now 3.0.14-1ubuntu1 all [installed]
php7.0-common/xenial-updates,xenial-security,now 7.0.4-7ubuntu2.1 amd64
[installed,automatic]
php7.0-gd/xenial-updates,xenial-security,now 7.0.4-7ubuntu2.1 amd64
[installed,automatic]
I believe