pgsql: Fix compilation with older OpenSSL versions

Fix compilation with older OpenSSL versions

Some older OpenSSL versions (0.9.8 branch) define TLS*_VERSION macros
but not the corresponding SSL_OP_NO_* macro, which causes the code for
handling ssl_min_protocol_version/ssl_max_protocol_version to fail to
compile. To fix, add more #ifdefs and error handling.

Reported-by: Victor Wagner <vitus(at)wagner(dot)pp(dot)ru>
Reviewed-by: Michael Paquier <michael(at)paquier(dot)xyz>
Discussion: https://www.postgresql.org/message-id/flat/20190924101859.09383b4f%40fafnir.local.vm

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/a430c7b4afe8278223541d3efee2281ee9135c1d

Modified Files
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src/backend/libpq/be-secure-openssl.c | 48 +++++++++++++++++++++++++++++++++--
1 file changed, 46 insertions(+), 2 deletions(-)