replace print_hidden with hidden_tag

classes/pref/feeds.php

classes/pref/filters.php

plugins/af_proxy_http/init.php

plugins/af_psql_trgm/init.php

plugins/af_readability/init.php

plugins/af_redditimgur/init.php

plugins/mail/init.php

plugins/note/init.php

plugins/nsfw/init.php