undefined reference to 'pg_detoast_datum'

In PostgreSQL 7.2 (Redhat 7.3 version, so it is patched), I'm trying to
create a Version-1 C server extension. The Version-0 format works, the
Version-1 version fails with:
undefined reference to 'pg_detoast_datum'

According to docs at:
http://www.postgresql.org/docs/7.2/interactive/xfunc-c.html

...by using Version-1 the pg_detoast_datum is no longer needed. FYI, the
function being created takes and returns a text argument. Are the docs
there wrong, or is there a bug in the library build, that causes
Version-1 to require linking to a lib with pg_detoast_datum?

A google search shows very little concerning the pg_detoast_datum
undefined reference link error. It is looking more like the V1 has to be
skipped and I'll have to go back to V0 if I can't get this to work. [and
unless someone can magically make the default PostgreSQL version on RH
7.3 change to a newer version of PostgreSQL, then a newer version can't
be used]

D. Stimits