Allow the bhyve VNC server to listen on IPv6 for incoming connections.

Alternatively to IPv4 address:port this will allow to listen on IPv6
link-local (incl. scope), a specific address, or ::. Addresses have
to be given in RFC2732 format so that [::]:port parsing will work.

This patch also starts to introduce WITH_INET/INET6_SUPPORT to bhyve.

PR: 232018
Submitted by: Dave Rush (northwoodlogic.free gmail.com) (original)
Reviewed by: Dave Rush (updated verison)
MFC after: 3 days