how to enable ldap authentication

I was trying to enable ldap authentication for 9.1 server.
I did:
./configure --with-ldap --with-openssl
make
sudo make install

And got these files installed:
ll /usr/local/pgsql/bin/

-rwxr-xr-x 1 root root 54811 Oct 24 10:27 clusterdb
-rwxr-xr-x 1 root root 55860 Oct 24 10:27 createdb
-rwxr-xr-x 1 root root 58885 Oct 24 10:27 createlang
-rwxr-xr-x 1 root root 59094 Oct 24 10:27 createuser
-rwxr-xr-x 1 root root 54438 Oct 24 10:27 dropdb
-rwxr-xr-x 1 root root 58811 Oct 24 10:27 droplang
-rwxr-xr-x 1 root root 54440 Oct 24 10:27 dropuser
-rwxr-xr-x 1 root root 712806 Oct 24 10:27 ecpg
-rwxr-xr-x 1 root root 81110 Oct 24 10:27 initdb
-rwxr-xr-x 1 root root 42019 Oct 24 10:27 pg_basebackup
-rwxr-xr-x 1 root root 30484 Oct 24 10:27 pg_config
-rwxr-xr-x 1 root root 26557 Oct 24 10:27 pg_controldata
-rwxr-xr-x 1 root root 40733 Oct 24 10:27 pg_ctl
-rwxr-xr-x 1 root root 323414 Oct 24 10:27 pg_dump
-rwxr-xr-x 1 root root 76002 Oct 24 10:27 pg_dumpall
-rwxr-xr-x 1 root root 34863 Oct 24 10:27 pg_resetxlog
-rwxr-xr-x 1 root root 141783 Oct 24 10:27 pg_restore
-rwxr-xr-x 1 root root 5524481 Oct 24 10:27 postgres
lrwxrwxrwx 1 root root 8 Oct 24 10:27 postmaster -> postgres
-rwxr-xr-x 1 root root 414148 Oct 24 10:27 psql
-rwxr-xr-x 1 root root 56027 Oct 24 10:27 reindexdb
-rwxr-xr-x 1 root root 33659 Oct 24 10:27 vacuumdb

It seemed the executable was compiled with ldap:

ldd /usr/local/pgsql/bin/postgres
libpam.so.0 => /lib64/libpam.so.0 (0x0000003d12300000)
libssl.so.0.9.8 => /usr/lib/libssl.so.0.9.8 (0x0000003d10200000)
libcrypto.so.0.9.8 => /usr/lib/libcrypto.so.0.9.8 (0x0000003d10c00000)
libgssapi_krb5.so.2 => /usr/lib64/libgssapi_krb5.so.2 (0x0000003d11200000)
libcrypt.so.1 => /lib64/libcrypt.so.1 (0x0000003d10600000)
libdl.so.2 => /lib64/libdl.so.2 (0x0000003d10000000)
libm.so.6 => /lib64/tls/libm.so.6 (0x0000002a95567000)
libldap-2.2.so.7 => /usr/lib64/libldap-2.2.so.7 (0x0000002a956ed000) <----
libc.so.6 => /lib64/tls/libc.so.6 (0x0000003d0fd00000)
libaudit.so.0 => /lib64/libaudit.so.0 (0x0000003d11f00000)
libkrb5.so.3 => /usr/lib64/libkrb5.so.3 (0x0000003d11600000)
libk5crypto.so.3 => /usr/lib64/libk5crypto.so.3 (0x0000003d11000000)
libcom_err.so.2 => /lib64/libcom_err.so.2 (0x0000002a95825000)
/lib64/ld-linux-x86-64.so.2 (0x0000003d0fb00000)
liblber-2.2.so.7 => /usr/lib64/liblber-2.2.so.7 (0x0000002a95927000)
libresolv.so.2 => /lib64/libresolv.so.2 (0x0000003d10a00000)
libsasl2.so.2 => /usr/lib64/libsasl2.so.2 (0x0000002a95a36000)
libssl.so.4 => /lib64/libssl.so.4 (0x0000003d10800000)
libcrypto.so.4 => /lib64/libcrypto.so.4 (0x0000003d11800000)
libz.so.1 => /usr/lib64/libz.so.1 (0x0000003d10400000)

ldd /usr/local/pgsql/bin/pg_ctl
libpq.so.5 => /usr/local/pgsql/lib/libpq.so.5 (0x0000002a95557000)
libpam.so.0 => /lib64/libpam.so.0 (0x0000003d12300000)
libssl.so.0.9.8 => /usr/lib/libssl.so.0.9.8 (0x0000003d10200000)
libcrypto.so.0.9.8 => /usr/lib/libcrypto.so.0.9.8 (0x0000003d10c00000)
libgssapi_krb5.so.2 => /usr/lib64/libgssapi_krb5.so.2 (0x0000003d11200000)
libz.so.1 => /usr/lib64/libz.so.1 (0x0000003d10400000)
libreadline.so.4 => /usr/lib64/libreadline.so.4 (0x0000003d11400000)
libtermcap.so.2 => /lib64/libtermcap.so.2 (0x0000002a9568f000)
libcrypt.so.1 => /lib64/libcrypt.so.1 (0x0000003d10600000)
libdl.so.2 => /lib64/libdl.so.2 (0x0000003d10000000)
libm.so.6 => /lib64/tls/libm.so.6 (0x0000002a95793000)
libc.so.6 => /lib64/tls/libc.so.6 (0x0000003d0fd00000)
libldap_r-2.2.so.7 => /usr/lib64/libldap_r-2.2.so.7 (0x0000002a9591a000) <------
libpthread.so.0 => /lib64/tls/libpthread.so.0 (0x0000002a95a59000)
libaudit.so.0 => /lib64/libaudit.so.0 (0x0000003d11f00000)
libkrb5.so.3 => /usr/lib64/libkrb5.so.3 (0x0000003d11600000)
libk5crypto.so.3 => /usr/lib64/libk5crypto.so.3 (0x0000003d11000000)
libcom_err.so.2 => /lib64/libcom_err.so.2 (0x0000002a95b70000)
/lib64/ld-linux-x86-64.so.2 (0x0000003d0fb00000)
liblber-2.2.so.7 => /usr/lib64/liblber-2.2.so.7 (0x0000002a95c72000)
libresolv.so.2 => /lib64/libresolv.so.2 (0x0000003d10a00000)
libsasl2.so.2 => /usr/lib64/libsasl2.so.2 (0x0000002a95d81000)
libssl.so.4 => /lib64/libssl.so.4 (0x0000003d10800000)
libcrypto.so.4 => /lib64/libcrypto.so.4 (0x0000003d11800000)

But when I ran pg_ctl start, it exits without listening any port and I got this:
tail postgresql-2011-10-24_104954.log
LOG: invalid authentication method "ldap": not supported by this build
CONTEXT: line 97 of configuration file "/usr/local/pgsql/databases/tudouapi/pg_hba.conf"
FATAL: could not load pg_hba.conf

Anyone be so kind to enlighten me !!