pgsql: Modify psql's \d printout to fold exclusion constraints in with

Log Message:
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Modify psql's \d printout to fold exclusion constraints in with regular
indexes, rather than printing them twice.  Per my gripe when the exclusion
constraint feature was committed.

Modified Files:
--------------
    pgsql/src/bin/psql:
        describe.c (r1.240 -> r1.241)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/describe.c?r1=1.240&r2=1.241)