switching on libxml

Hello,
I am running Postgres 8.3.0 on RHEL 4, and trying to insert a value into an xml data type:

create table test_xml (name character varying(10), iteminfo xml)
insert into test_xml values ('bob', 'xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance')

I get the following error message:

ERROR: unsupported XML feature
DETAIL: This functionality requires the server to be built with libxml support.
HINT: You need to rebuild PostgreSQL using --with-libxml.

Is there a way to "switch on" the libxml option after a db cluster has been instantiated? Or do I really need to rebuild postgres with the --with-libxml parameter?

Thank you,
Sincerely,
Kasia