Enabling Multibyte in postgresql / drupal Mac OS X Leopard stack

I recently downloaded and installed postgresql and drupal and
mediawiki for Mac OS Leopard, using the stack from postgresql.org.

It is very cool!

However, the drupal admin states that php multibyte strings (mbstring)
is not enabled.
I tried following the instructions on various searches, without success.

If any one has been able to enable php mbstring on Mac OS Leopard php
for drupal / mediawiki, using postgresql as their dbs, please let me
know.

Any information would be much appreciated.

thanks

--
-jeroen