pgsql: Add configuration parameter ssl_renegotiation_limit to control

Log Message:
-----------
Add configuration parameter ssl_renegotiation_limit to control
how often we do SSL session key renegotiation. Can be set to
0 to disable renegotiation completely, which is required if
a broken SSL library is used (broken patches to CVE-2009-3555
a known cause) or when using a client library that can't do
renegotiation.

Tags:
----
REL8_4_STABLE

Modified Files:
--------------
    pgsql/doc/src/sgml:
        config.sgml (r1.220.2.1 -> r1.220.2.2)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml?r1=1.220.2.1&r2=1.220.2.2)
    pgsql/src/backend/libpq:
        be-secure.c (r1.92.2.2 -> r1.92.2.3)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/libpq/be-secure.c?r1=1.92.2.2&r2=1.92.2.3)
    pgsql/src/backend/utils/misc:
        guc.c (r1.505.2.4 -> r1.505.2.5)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c?r1=1.505.2.4&r2=1.505.2.5)
        postgresql.conf.sample (r1.260.2.1 -> r1.260.2.2)

(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/postgresql.conf.sample?r1=1.260.2.1&r2=1.260.2.2)