pgsql: Document that pg_getaddrinfo_all does not accept null hints

Document that pg_getaddrinfo_all does not accept null hints

While the underlying getaddrinfo call accepts a null pointer for
the hintp parameter, pg_getaddrinfo_all does not.  Document this
difference with a comment to make it clear.

Author: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reported-by: Sergey Tatarintsev <s.tatarintsev@postgrespro.ru>
Discussion: https://postgr.es/m/1e5efc94-407e-40b8-8b10-4d25f823c6d7@postgrespro.ru

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/d22cc7326ce0fe5033f2c6e3f711047d263c1c86

Modified Files
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src/common/ip.c | 3 +++
1 file changed, 3 insertions(+)