pgpool: Fix handling of negotiate protocol version message.

Fix handling of negotiate protocol version message.

ProcessNegotiateProtocol() saves NegotiateProtocolVersion message in a
Startup packet (sp->negotiateProtocolMsg) when initial connection to
backend is established. Unfortunately there was a bug with it.
Actually part of the message (unsupported optional messages) was not
saved. This prevented reusing the connection if frontend actually
checks unsupported optional messages are in the NegotiateProtocol
message.

This was discovered in PostgreSQL 19 beta while "greasing".
https://www.postgresql.org/message-id/DDZ539Z6JWSB.1BF62QDLBANQA%40jeltef.nl

Branch
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master

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=7bcb55898a9a1fbac39dcecf5c9762f38213237f

Modified Files
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src/auth/pool_auth.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)