pgsql: Document the exponentiation operator as associating left to righ

Document the exponentiation operator as associating left to right.

Common mathematical convention is that exponentiation associates right to
left.  We aren't going to change the parser for this, but we could note
it in the operator's description.  (It's already noted in the operator
precedence/associativity table, but users might not look there.)
Per bug #13829 from Henrik Pauli.

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/4388895a65aa71961e885d8a292e95b70fd57ad8

Modified Files
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doc/src/sgml/func.sgml |    2 +-
1 file changed, 1 insertion(+), 1 deletion(-)