simulate domain http request

change input format, add domain and separate by semicolon. while
requesting, the host of HTTP packet sent to is the domain name.
add new line at the end of the file

add new line at the end of the file, avoid compile warning
change cooldown parameter to microsecond

In some case, you scan a small number of hosts. do not need to wait in
seconds, change to microsecond, decrease wait time.
modify in my environment

gcc version 4.4.7
gcc do not known -Werror
libpcap-devel-0.9.4-15.el5
pcap install in /usr/local/include, do not have pcap directory