pgsql: Support SSL certificate chains in the server certificate file.

Log Message:
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Support SSL certificate chains in the server certificate file.

Andrew Gierth

Modified Files:
--------------
pgsql/src/backend/libpq:
be-secure.c (r1.90 -> r1.91)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/be-secure.c?r1=1.90&r2=1.91)