it's defined:
create or replace function filter_text(text, char) returns text as
'test_proc.so' language 'c';
which leads me to another question.
It seems that I have to leave psql and comeback, for new version to be
loaded. (that's on 8.4 tho, I don't have 8.3 at home).
And also that 'replace' bit doesn't seem to actually refresh it either.