BUG #1491: Getting an "undefined symbol" when loading contrib mod.

The following bug has been logged online:

Bug reference:      1491
Logged by:          Alexis Wilke
Email address:      alexis@m2osw.com
PostgreSQL version: 8.0.1
Operating system:   Linux
Description:        Getting an "undefined symbol" when loading contrib mod.
Details:

I'm trying to use ltree to sort one of my table using a tree like column
("1", "1.1", "1.2", "2", "2.1", etc.)

Everything compiles, after my fix to the .sql.in -> .sql convertion
($(libdir) instead of $$libdir in pgxs.mk) and everything also seems to be
installed properly.

However, in version 7.4.6 and version 8.0.1, when I try to load the module,
it says it can't find the symbol errstart (one of the elog functions better
known as ereport).

There are a few versions if that helps at all...

   gcc (GCC) 3.4.3

   GNU ld version 2.13.90.0.18 20030206

   ldd (GNU libc) 2.3.2

There is the complete message I'm getting from postgres

crm=> SET search_path = public;
SET
crm=> CREATE FUNCTION ltree_in(cstring)
crm-> RETURNS ltree
crm-> AS '/usr/local/pgsql/lib/ltree'
crm-> LANGUAGE 'C' WITH (isstrict);
NOTICE:  ProcedureCreate: type ltree is not yet defined
ERROR:  Load of file /usr/local/pgsql/lib/ltree.so failed:
/usr/local/pgsql/lib/ltree.so: undefined symbol: errstart