To install the trigger do the following:

# cp Makefile-dist Makefile

# edit Makefile
(and change pathnames and PGVERSION if neccessary).

# make
(This makes the trigger binary and places it in INSTALLDIR with permissions 644)

# edit postgresql.script
(And change the path to dupetrigger.so to INSTALLDIR)

# psql -U postgres Mir < postgresql.script
(This installs the the trigger binary and creates a new trigger.)