pgsql: Reduce contrib/intagg to a thin wrapper around the new core

Log Message:
-----------
Reduce contrib/intagg to a thin wrapper around the new core functions
array_agg() and unnest().  We could drop it entirely in the future,
but let's keep it for a release or two as a compatibility assist.

Modified Files:
--------------
    pgsql/contrib/intagg:
        Makefile (r1.9 -> r1.10)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/intagg/Makefile?r1=1.9&r2=1.10)
        uninstall_int_aggregate.sql (r1.3 -> r1.4)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/intagg/uninstall_int_aggregate.sql?r1=1.3&r2=1.4)
    pgsql/doc/src/sgml:
        intagg.sgml (r1.3 -> r1.4)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/intagg.sgml?r1=1.3&r2=1.4)

Added Files:
-----------
    pgsql/contrib/intagg:
        int_aggregate.sql (r1.1)

(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/intagg/int_aggregate.sql?rev=1.1&content-type=text/x-cvsweb-markup)

Removed Files:
-------------
    pgsql/contrib/intagg:
        int_aggregate.c
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/intagg/int_aggregate.c)
        int_aggregate.sql.in
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/intagg/int_aggregate.sql.in)