Italian language update

inc/lang/it/subscr_form.txt

inc/lang/it/subscr_list.txt

inc/lang/it/subscr_single.txt

inc/lang/it/uploadmail.txt

inc/lang/it/wordblock.txt

lib/plugins/acl/lang/it/help.txt

lib/plugins/acl/lang/it/lang.php

lib/plugins/config/lang/it/lang.php

lib/plugins/plugin/lang/it/admin_plugin.txt

lib/plugins/plugin/lang/it/lang.php

lib/plugins/popularity/lang/it/intro.txt

lib/plugins/revert/lang/it/intro.txt

lib/plugins/usermanager/lang/it/delete.txt

lib/plugins/usermanager/lang/it/lang.php