pgsql: Documentation fix: sum(float4) returns float4, not float8.

Documentation fix: sum(float4) returns float4, not float8.

The old claim is from my commit d06ebdb8d3425185d7e641d15e45908658a0177d of
2000-07-17, but it seems to have been a plain old thinko; sum(float4) has
been distinct from sum(float8) since Berkeley days.  Noted by KaiGai Kohei.

While at it, mention the existence of sum(money), which is also of
embarrassingly ancient vintage.

Branch
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REL9_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/b1a7c9e387f77b85aa14eb342f0432fcdb6ddc35

Modified Files
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doc/src/sgml/func.sgml |    7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)