Error message editing in backend/catalog.

src/backend/catalog/aclchk.c

src/backend/catalog/dependency.c

src/backend/catalog/heap.c

src/backend/catalog/index.c

src/backend/catalog/namespace.c

src/backend/catalog/pg_aggregate.c

src/backend/catalog/pg_constraint.c

src/backend/catalog/pg_conversion.c

src/backend/catalog/pg_largeobject.c

src/backend/catalog/pg_namespace.c

src/backend/catalog/pg_operator.c

src/backend/catalog/pg_proc.c

src/backend/catalog/pg_type.c

src/include/utils/acl.h

src/include/utils/elog.h

src/test/regress/expected/alter_table.out

src/test/regress/expected/conversion.out

src/test/regress/expected/create_type.out

src/test/regress/expected/domain.out

src/test/regress/expected/errors.out