pgsql: Go over all OpenSSL return values and make sure we compare them

Log Message:
-----------
Go over all OpenSSL return values and make sure we compare them
to the documented API value. The previous code got it right as
it's implemented, but accepted too much/too little compared to
the API documentation.

Per comment from Zdenek Kotala.

Tags:
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REL8_1_STABLE

Modified Files:
--------------
    pgsql/src/backend/libpq:
        be-secure.c (r1.59.2.3 -> r1.59.2.4)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/be-secure.c?r1=1.59.2.3&r2=1.59.2.4)
    pgsql/src/interfaces/libpq:
        fe-secure.c (r1.73.2.1 -> r1.73.2.2)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-secure.c?r1=1.73.2.1&r2=1.73.2.2)