enable [--arp] output mac addr to xml

[nixawk]

$ ./bin/masscan --arp --source-ip 192.168.53.141 --source-mac bc-ec-34-ac-e3-c3 192.168.53.0/24 -oX macaddr.xml

Starting masscan 1.0.3 (http://bit.ly/14GZzcT) at 2017-04-28 05:31:54 GMT
 -- forced options: -sS -Pn -n --randomize-hosts -v --send-eth
Initiating SYN Stealth Scan
Scanning 256 hosts [1 port/host]

$ head -10 macaddr.xml
<?xml version="1.0"?>
<!-- masscan v1.0 scan -->
<?xml-stylesheet href="" type="text/xsl"?>
<nmaprun scanner="masscan" start="1493357515" version="1.0-BETA"  xmloutputversion="1.03">
<scaninfo type="syn" protocol="tcp" />
<host endtime="1493357514"><address addr="192.168.53.79" addrtype="ipv4"/><ports><port protocol="arp" portid="0"><state state="up" reason="none" reason_ttl="0"/></port></ports><mac addr="f4:5c:89:ae:6e:a1"></host>
<host endtime="1493357514"><address addr="192.168.53.26" addrtype="ipv4"/><ports><port protocol="arp" portid="0"><state state="up" reason="none" reason_ttl="0"/></port></ports><mac addr="a0:86:c6:3b:e8:e5"></host>
<host endtime="1493357515"><address addr="192.168.53.89" addrtype="ipv4"/><ports><port protocol="arp" portid="0"><state state="up" reason="none" reason_ttl="0"/></port></ports><mac addr="48:a1:95:1d:17:ce"></host>
<host endtime="1493357515"><address addr="192.168.53.4" addrtype="ipv4"/><ports><port protocol="arp" portid="0"><state state="up" reason="none" reason_ttl="0"/></port></ports><mac addr="ac:bc:32:d6:7d:bf"></host>
<host endtime="1493357515"><address addr="192.168.53.152" addrtype="ipv4"/><ports><port protocol="arp" portid="0"><state state="up" reason="none" reason_ttl="0"/></port></ports><mac addr="10:2a:b3:98:78:01"></host>