The only way I've found to get hibernate, and suspend to work at KDM is to add two 'sessions' to the session selector menu.
That is, where you select KDE, XFCE, etc.
Having sudo set up properly for the respective user accounts you wish to invoke the suspend/hibernate will then allow the suspend, and hibernate to be selected as your session, then you just enter your username and pass as you would normally do to login, and the pc will suspend or hibernate accordingly.
Just add the two desktop entries in /usr/share/apps/kdm/sessions
I named mine suspend.desktop and hibernate.desktop accordingly.
If you don't want to reboot, I'd just telinit 3 ; telinit 4 from ctl-alt-f6 and KDM should see them (logout and save work first
. I don't think update-desktop-database' is needed iirc.
Comment=Suspends the computer
Comment=hibernate the computer
If anyone knows a better way, I *truly* am all ears. Especially if someone knows a good keybind, such as the ctrl-alt-del listed in Slackware's init scripts.