sFlow: add Sun Industry Standards Source License 1.1 as licensing option

sFlow: add Sun Industry Standards Source License 1.1 as licensing option

The sFlow License was not on the list for the Fedora Project,  but the
Sun Industry Standards Source License 1.1 was (and it has the right
properties).  So this patch includes it as a licensing option in the
relevant places (COPYING and the lib/sflow* sources).   Let me know
if this looks OK or not.

Signed-off-by: Neil McKee <neil.mckee@inmon.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Chris Wright <chrisw@sous-sol.org>