iproute: Add ability to save, restore and show the interfaces' addresses (resend)

iproute: Add ability to save, restore and show the interfaces' addresses (resend)

This functionality is required by checkpoint-restore project. Since the
dump and restore for routes is already done in ip tool it's naturally to
dump and restore addresses in the ip tool as well.

The implementation logic is the same as for the respective one for routes.
The magic number digits are taken from the Seattle coordinates.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>