pgsql: Cleanup the contrib/lo module: there is no need anymore to

Log Message:
-----------
Cleanup the contrib/lo module: there is no need anymore to implement
a physically separate type. Defining 'lo' as a domain over OID works
just fine and is more efficient. Improve documentation and fix up the
test script. (Would like to turn test script into a proper regression
test, but right now its output is not constant because of numeric OIDs;
plus it makes Unix-specific assumptions about files it can import.)

Modified Files:
--------------
pgsql/contrib/lo:
README.lo (r1.1 -> r1.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/lo/README.lo.diff?r1=1.1&r2=1.2)
lo.c (r1.14 -> r1.15)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/lo/lo.c.diff?r1=1.14&r2=1.15)
lo.sql.in (r1.12 -> r1.13)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/lo/lo.sql.in.diff?r1=1.12&r2=1.13)
lo_drop.sql (r1.4 -> r1.5)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/lo/lo_drop.sql.diff?r1=1.4&r2=1.5)
lo_test.sql (r1.2 -> r1.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/lo/lo_test.sql.diff?r1=1.2&r2=1.3)
pgsql/contrib/vacuumlo:
README.vacuumlo (r1.4 -> r1.5)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/vacuumlo/README.vacuumlo.diff?r1=1.4&r2=1.5)