Unless I'm going crazy or have missed the point, you've accidentally snipped
the:

install: all installdirs

line from

slony1-engine/src/xxid/Makefile

while adding the DESTDIR edits between version 1.8 and 1.9 (unfortunately
between RC1 and the Release).  So xxid.so doesn't get installed (I haven't
tried it with a raw make install, I've only tried making an RPM -- it spots
the missing file).

Hope that helps

Julian Scarfe