netsock2: ast_addressfamily_to_sockaddrsize and ast_sockaddr_from_sockaddr.

ast_addressfamily_to_sockaddrize will determine the size that's
required, and ast_sockaddr_from_sockaddr then wraps this new function
and ast_sockaddr_copy_sockaddr to copy arbitrary sockaddr's (without
knowing the address family) into the ast_sockaddr structure.

Change-Id: Iee604e96e9096c79b477d6e5ff310cf0b06dae86
Signed-off-by: Jaco Kroon <jaco@uls.co.za>