Attempts to get the hostname from an IP address.

• Attempts to use shell_exec first since you can set timeout limits that way
• Determines what command to send based on whether or not you're on a Windows host (nslookup for Windows or host for others)
• shell_exec usage is random depending on the outcome of rand(0,1)
• Sets the "host_to_dis" setting to 1 if the "-W" option on the host command returns "invalid option"
• Uses gethostbyaddr as a last resort