rsyslog: parseLegacySyslogMsg off-by-two buffer overflow

Stack-based buffer overflow in the parseLegacySyslogMsg function in tools/syslogd.c in rsyslogd in rsyslog 4.6.x before 4.6.8 and 5.2.0 through 5.8.4 might allow remote attackers to cause a denial of service application exit via a long TAG in a legacy syslog message...