fix bug #64124 (IPv6 malformed)

hostname returned from zend_parse_parameters() was modified in
netsnmp_session_init() that caused imput parameter modification along with
unpredictable changes when parameter is a constant sctring.

One typo in comment was fixed.
Merge branch 'PHP-5.4' of https://git.php.net/push/php-src into PHP-5.4