pgsql: More clearly document that most PostgreSQL utilities support

Log Message:
-----------
More clearly document that most PostgreSQL utilities support libpq
environment variables.  Backpatch to 8.2.X.

Tags:
----
REL8_2_STABLE

Modified Files:
--------------
    pgsql/doc/src/sgml/ref:
        clusterdb.sgml (r1.18 -> r1.18.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/clusterdb.sgml.diff?r1=1.18&r2=1.18.2.1)
        createdb.sgml (r1.42 -> r1.42.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/createdb.sgml.diff?r1=1.42&r2=1.42.2.1)
        createlang.sgml (r1.38 -> r1.38.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/createlang.sgml.diff?r1=1.38&r2=1.38.2.1)
        createuser.sgml (r1.45 -> r1.45.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/createuser.sgml.diff?r1=1.45&r2=1.45.2.1)
        dropdb.sgml (r1.28 -> r1.28.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/dropdb.sgml.diff?r1=1.28&r2=1.28.2.1)
        droplang.sgml (r1.27 -> r1.27.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/droplang.sgml.diff?r1=1.27&r2=1.27.2.1)
        dropuser.sgml (r1.34 -> r1.34.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/dropuser.sgml.diff?r1=1.34&r2=1.34.2.1)
        initdb.sgml (r1.37 -> r1.37.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/initdb.sgml.diff?r1=1.37&r2=1.37.2.1)
        pg_controldata.sgml (r1.8 -> r1.8.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/pg_controldata.sgml.diff?r1=1.8&r2=1.8.2.1)
        pg_ctl-ref.sgml (r1.35 -> r1.35.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/pg_ctl-ref.sgml.diff?r1=1.35&r2=1.35.2.1)
        pg_dump.sgml (r1.92 -> r1.92.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/pg_dump.sgml.diff?r1=1.92&r2=1.92.2.1)
        pg_dumpall.sgml (r1.58.2.1 -> r1.58.2.2)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/pg_dumpall.sgml.diff?r1=1.58.2.1&r2=1.58.2.2)
        pg_restore.sgml (r1.64 -> r1.64.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/pg_restore.sgml.diff?r1=1.64&r2=1.64.2.1)
        psql-ref.sgml (r1.175.2.3 -> r1.175.2.4)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/psql-ref.sgml.diff?r1=1.175.2.3&r2=1.175.2.4)
        reindexdb.sgml (r1.2 -> r1.2.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/reindexdb.sgml.diff?r1=1.2&r2=1.2.2.1)
        vacuumdb.sgml (r1.37 -> r1.37.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/vacuumdb.sgml.diff?r1=1.37&r2=1.37.2.1)