slackware doesn't ship with PAM.
there is an external project developed by Vincent Batts that aims to pamify Slackware
http://www.slackware.com/~vbatts/pam/
but the sources and packages are updated for Slackware-14.0, so if you want to use those you have to install 14.0 (or you have to port them yourself to 14.1).