emulators/virtualbox-ose{,-nox11}{,-legacy}: Fix listen VNC on TCP port on IPv6 address

Four new options are available:
 - "VNCAddress4" -> IPv4 address to use
 - "VNCPort4" -> IPv4 Port to use
 - "VNCAddress6" -> IPv6 address to use
 - "VNCPort6" -> IPv6 port to use

"TCP/Ports" is used for backward compatibility as IPv4 and IPv6 ports if
"VNCPort4" or "VNCPort6" is not defined.

Detailed description is here:
https://www.virtualbox.org/browser/vbox/trunk/src/VBox/ExtPacks/VNC/VBoxVNC.cpp#L361

PR:	193778