Update with changes from upstream and add --send-client-ip option.

Hi xrm,

this will pull the latest changes from upstream (kanaka/websockify) into your master and will include my quick&dirty support for reporting the client IP to the target (mud).
The approach is certainly improvable, but the manner of reporting/forwarding works for us in Morgengrauen for some years with different proxies and basically for some months with websockify.

Have fun,
Zesstra