pgsql: Suppress integer-overflow compiler warning for inconsistent sun_

Suppress integer-overflow compiler warning for inconsistent sun_len.

On AIX 7.1, struct sockaddr_un is declared to be 1025 bytes long,
but the sun_len field that should hold the length is only a byte.
Clamp the value we try to store to ensure it will fit in the field.

(This coding might need adjustment if there are any machines out
there where sun_len is as wide as size_t; but a preliminary survey
suggests there's not, so let's keep it simple.)

Discussion: https://postgr.es/m/2781112.1644819528@sss.pgh.pa.us

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/291ec6e45ebe1a87f930a250ad3c6672472b9b19

Modified Files
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src/common/ip.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)