Add SocketAddressInformation for IPv6 support

[Rinzwind]

This pull request adds SocketAddressInformation and some auxiliary methods on Socket, copied from Squeak 6.1 alpha 22998, to allow making use of SocketPlugin’s IPv6 support. The methods #primSocket:bindTo: and #primSocket:connectTo: in Socket’s protocol ‘primitives - ipv6’ previously had no senders.

With SocketAddressInformation, a listening socket using IPv6 can be set up as follows:

addressInformations := SocketAddressInformation forHost: ''
	service: 2000 asString
	flags: SocketAddressInformation passiveFlag
	addressFamily: SocketAddressInformation addressFamilyINET6
	socketType: SocketAddressInformation socketTypeStream
	protocol: SocketAddressInformation protocolTCP.
listeningSocket := addressInformations first listenWithBacklog: 5.
[
	acceptedSocket := listeningSocket waitForAcceptFor: 300.
	Transcript show: 'Received data: ' , acceptedSocket receiveData; cr.
	acceptedSocket close.
	listeningSocket close.
] fork.

It can then be connected to as follows:

addressInformations := SocketAddressInformation forHost: ''
	service: 2000 asString
	flags: 0
	addressFamily: SocketAddressInformation addressFamilyINET6
	socketType: SocketAddressInformation socketTypeStream
	protocol: SocketAddressInformation protocolTCP.
connectedSocket := addressInformations first connect.
connectedSocket sendData: DateAndTime now asString; close.

A motivation for this pull request is the problem I encountered with Safari in Pharo VM pull request #816 when using IPv4.

[Ducasse]

@tesonep I propose to merge it.