pgsql: Fix error message for COMMENT/SECURITY LABEL ON COLUMN xxx IS 'y

Fix error message for COMMENT/SECURITY LABEL ON COLUMN xxx IS 'yyy'

When the column name is an unqualified name, rather than table.column,
the error message complains about too many dotted names, which is
wrong. Report by Peter Eisentraut based on examination of the
sepgsql regression test output, but the problem also affects COMMENT.
New wording as suggested by Tom Lane.

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/ae7c8b290f525504978c01d77366a753505d10d5

Modified Files
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contrib/sepgsql/expected/label.out | 2 +-
src/backend/catalog/objectaddress.c | 4 ++++
src/test/regress/input/security_label.source | 1 +
src/test/regress/output/security_label.source | 2 ++
4 files changed, 8 insertions(+), 1 deletions(-)