IPv6 support for Parrot

[mstapelberg]

Extract from the commit message:

connect() and bind() use an Addrinfo PMC (contains multiple socket
addresses in the right order [RFC 3484]) instead of a Sockaddr PMC.
It is no longer necessary to create the socket before calling bind()
or connect() as both need to create sockets with the appropriate
address family on their own.

Also, the Sockaddr PMC internally uses a struct sockaddr_storage
in combination with a length field instead of an struct sockaddr_in.

This commit also implements the local_address and remote_address
methods for the Socket PMC. The Sockaddr PMC can now be converted
to string.

[dukeleto]

Very exciting patch! I've talked with the author on #parrot and asked for some tests and additions to docs in the docs/ directory. After some tests are added, we should test this patch on a few platforms and if it works well, apply it!

[dukeleto]

I've started a branch for this patch here:

 https://github.com/parrot/parrot/tree/tt1798_ipv6

[dukeleto]

This branch has been merged.