Обсуждение: pgsql: Doc: update libpq's documentation for PQfn().

Doc: update libpq's documentation for PQfn().

Mention specifically that you can't call aggregates, window functions,
or procedures this way (the inability to call SRFs was already
mentioned).

Also, the claim that PQfn doesn't support NULL arguments or results
has been a lie since we invented protocol 3.0.  Not sure why this
text was never updated for that, but do it now.

Discussion: https://postgr.es/m/2039442.1615317309@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/386e64ea5abf346d887c21ea8869317838ba19b5

Modified Files
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doc/src/sgml/libpq.sgml | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)