TODO:
 * mail notification when specific (critical) IPs changes occur. Example: DNS or gateway (-> conf file)
 * rewrite/rearrange code files more cleanly
 * CPP flags are not correct (-w inhibits all warning messages...), gotta change this

On the way:
 * default daemon mode --> with logging in a specific file (such as /var/log/arphound.log) with rotate&co <-- and no output (normal mode with option like '-nd' 'no daemon')
 * finish and test init.d script
