Currently, we pass around sockaddr to various locations where they
might case things to IPv4 or IPv6 addresses.  In the latter case,
this struct is not large enough to hold an IPv6 address, so we end
up smashing the stack.

For example:
	ifconfig sit1 inet6 pointopoint ::1.2.3.4
This calls ap->input() with an IPv6 address but a sockaddr struct.
Internally, we cast this to sockaddr_in6 and then write too much.

Rather than fixing this one cast, change the code to use the new
sockaddr_storage struct.  Then point sockaddr_in and sockaddr_in6
to that location.  This way we can use "sa" everywhere and then
use "sin" and "sin6" automatically (since they point to the same
storage).

URL: http://sourceforge.net/p/net-tools/bugs/3/Signed-off-by: Mike Frysinger <vapier@gentoo.org>