Should have some way to bind to specific IP(v6) address

[ahupowerdns]

Don't get me wrong with all these tickets, they are because I like what I am seeing. I might also PR this up. But, only binding to a 'port' is going to cause immediate problems for my use of Silicon. I checked out the microhttpd way to do this and it is quite nice, but it does not immediately fit on mhd_json_serve, unless we accept an IP address as a string in which case it is rather easy.

Thoughts?

[matt-42]

Indeed, passing a string instead of a port will be nice to handle ipv4 and ipv6 address. I'll add this to the MHD backend. Thanks again, your feedback is more than welcome.