pgsql: Docs: fix misleading example.

Docs: fix misleading example.

Commit 8457d0beca731bf0 introduced an example which, while not incorrect,
failed to exhibit the behavior it meant to describe, as a result of omitting
an E'' prefix that needed to be there.  Noticed and fixed by Peter Geoghegan.

I (tgl) failed to resist the temptation to wordsmith nearby text a bit
while at it.

Branch
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REL9_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/ff4adfd27ca6cbb94512c2433c086eba6ad97019

Modified Files
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doc/src/sgml/datatype.sgml |    9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)