BUG #2301: xml2 library not running on the Win Pg 8.1

The following bug has been logged online:

Bug reference:      2301
Logged by:          Balázs Klein
Email address:      Balazs.Klein@axelero.hu
PostgreSQL version: 8.1
Operating system:   WinXP
Description:        xml2 library not running on the Win Pg 8.1
Details:

I have raised this issue in the pgsql.general newsgroup, Subject: installing
xml2 for pg 8.1 on winxp, but as I got no answers so far I am submitting
this as a bug.

There might be a problem with a missing extension in the pre-compiled
windows version of Postgres 8.1
It looks as though it's the 'MemoryContextSwitchTo' library which is
present in 8.0 but missing from 8.1.

I was trying to install the xml2 library to Postgres as I found it on
http://www.throwingbeans.org/postgresql_and_xml_updated.html but I had
no luck.

So I contacted Tom Dyson the author of the package and he informed me
that there were others having a similar problem with the 8.1 compile
while the library worked fine in the 8.0.3 version and he suggested that
based on e-mails he got the problem might be the one I mentioned above.

I just offered to report this problem of the build, unfortunately I
can't help much more as this is far too high level for me.

After placing the downloaded dll's to their places, the actual error I get
is:

When I run

CREATE OR REPLACE FUNCTION xml_valid(text) RETURNS bool AS
'libpgxml' LANGUAGE 'c' WITH (isStrict);

I got the error message
ERROR:  could not load library "C:/Program
Files/PostgreSQL/8.1/lib/libpgxml.dll": The specified procedure could
not be found.