PAM Authentication and Postgresql 7.3

I am trying to set up PAM authentication with postgres 7.3.1.  This is
under Mandrake Linux 8.2 for i586.  I've searched the archives and
haven't yet found a solution.
Here is the pg_hba.conf file:
--------------------------------
# TYPE  DATABASE    USER        IP-ADDRESS        IP-MASK
METHOD

local   all         all
trust
host    all         all         127.0.0.1         255.255.255.255
trust
host    all         all         0.0.0.0           0.0.0.0           pam
postgresql
--------------------------------

pg_config --configure shows this:
--------------------------------
'--prefix=/usr/local/pgsql' '--with-perl' '--with-pam'
'--with-openssl=/opt/openssl' '--without-readline'
'--with-libraries=/usr/lib:/lib:/usr/local/lib'
--------------------------------

And here is the error I am getting:
----------------------------------
2003-01-13 09:50:37 LOG:  connection received:
host=hc652a8a3.dhcp.vt.edu[198.82.168.163] port=33104
2003-01-13 09:50:37 LOG:  parse_hba: invalid syntax in pg_hba.conf file
at line 92, token "pam"
2003-01-13 09:50:37 FATAL:  Missing or erroneous pg_hba.conf file, see
postmaster log for details
----------------------------------

It looks like the server isn't recognizing the 'pam' keyword in
pg_hba.conf, but I can't figure out why this is happening.

--
Christopher L McNabb              Tel:   540 231 7554
Operating Systems Analyst         Email: cmcnabb@vt.edu
Virginia Tech                     ICBM:  37.205622N 80.414595W
GMRS: WPSR255                     ARS:   N2UX  Grid Sq: EM97SD