Arabic language update

inc/lang/ar/admin.txt

inc/lang/ar/denied.txt

inc/lang/ar/draft.txt

inc/lang/ar/lang.php

inc/lang/ar/mailtext.txt

inc/lang/ar/password.txt

inc/lang/ar/resendpwd.txt

inc/lang/ar/subscr_digest.txt

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

lib/plugins/acl/lang/ar/lang.php

lib/plugins/config/lang/ar/intro.txt

lib/plugins/config/lang/ar/lang.php

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

lib/plugins/plugin/lang/ar/lang.php

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

lib/plugins/popularity/lang/ar/lang.php

lib/plugins/revert/lang/ar/lang.php

lib/plugins/usermanager/lang/ar/lang.php