pgsql: Clarify some error messages about duplicate things.

Log Message:
-----------
Clarify some error messages about duplicate things.

Modified Files:
--------------
pgsql/src/backend/access/common:
reloptions.c (r1.4 -> r1.5)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/common/reloptions.c.diff?r1=1.4&r2=1.5)
pgsql/src/backend/access/nbtree:
nbtinsert.c (r1.157 -> r1.158)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/nbtree/nbtinsert.c.diff?r1=1.157&r2=1.158)
pgsql/src/backend/catalog:
heap.c (r1.321 -> r1.322)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/heap.c.diff?r1=1.321&r2=1.322)
pgsql/src/backend/commands:
tablecmds.c (r1.226 -> r1.227)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tablecmds.c.diff?r1=1.226&r2=1.227)
pgsql/src/test/regress/expected:
alter_table.out (r1.102 -> r1.103)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/alter_table.out.diff?r1=1.102&r2=1.103)
arrays.out (r1.33 -> r1.34)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/arrays.out.diff?r1=1.33&r2=1.34)
create_index.out (r1.24 -> r1.25)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/create_index.out.diff?r1=1.24&r2=1.25)
inherit.out (r1.20 -> r1.21)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/inherit.out.diff?r1=1.20&r2=1.21)
plpgsql.out (r1.54 -> r1.55)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/plpgsql.out.diff?r1=1.54&r2=1.55)
transactions.out (r1.15 -> r1.16)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/transactions.out.diff?r1=1.15&r2=1.16)
uuid.out (r1.2 -> r1.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/uuid.out.diff?r1=1.2&r2=1.3)
pgsql/src/test/regress/output:
constraints.source (r1.42 -> r1.43)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/output/constraints.source.diff?r1=1.42&r2=1.43)
tablespace.source (r1.4 -> r1.5)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/output/tablespace.source.diff?r1=1.4&r2=1.5)