minor auto_dl spacing update
Added detection for Errata Security's "Masscan" port scanner

Added detection for Errata Security's "Masscan" port scanner that was
used in an Internet-wide scan for port 22 on Sept. 12, 2013 (see:
http://blog.erratasec.com/2013/09/we-scanned-internet-for-port-22.html).
The detection strategy used by psad relies on the fact that masscan does
not appear to set the options portion of the TCP header, and if the
iptables LOG rules that generate log data for psad are built with the
--log-tcp-options switch, then no options in a SYN scan can be seen.
This is not to say that other scanning software always sets TCP options -
Scapy seems to not set options by default when issuing a SYN scan like
this either: http://www.secdev.org/projects/scapy/doc/usage.html#syn-scans
There is a new psad.conf variable "EXPECT_TCP_OPTIONS" to assist with
Masscan detection as well.  When looking for Masscan SYN scans, psad
requires at least one TCP options field to be populated within a LOG
message (so that it knows --log-tcp-options has been set for at least
some logged traffic), and after seeing this then SYN packets with no
options are attributed to Masscan traffic.  All usual psad threshold
variables continue to apply however, so (by default) a single Masscan
SYN packet will not trigger a psad alert.  Masscan detection can be
disabled altogether by setting EXPECT_TCP_OPTIONS to "N", and this will
not affect any other psad detection techniques such as passive OS
fingerprinting, etc.