pgsql: Remove sslverify parameter again, replacing it with two new

Log Message:
-----------
Remove sslverify parameter again, replacing it with two new sslmode values:
"verify-ca" and "verify-full".

Since "prefer" remains the default, this will make certificate validation
off by default, which should lead to less upgrade issues.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        libpq.sgml (r1.285 -> r1.286)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/libpq.sgml?r1=1.285&r2=1.286)
        runtime.sgml (r1.425 -> r1.426)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/runtime.sgml?r1=1.425&r2=1.426)
    pgsql/src/interfaces/libpq:
        fe-connect.c (r1.372 -> r1.373)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-connect.c?r1=1.372&r2=1.373)
        fe-secure.c (r1.123 -> r1.124)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/fe-secure.c?r1=1.123&r2=1.124)
        libpq-int.h (r1.140 -> r1.141)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/libpq-int.h?r1=1.140&r2=1.141)