ipv6: Add labels for site-local and 6bone testing addresses (RFC6724)

Added labels for site-local addresses (fec0::/10) and 6bone testing
addresses (3ffe::/16) in order to depreference them.

Note that the RFC introduced new rows for Teredo, ULA and 6to4 addresses
in the default policy table.  Some of them have different labels from ours.
For backward compatibility, we do not change the "default" labels.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>