flann: new package

[Thomas: changed license from BSD to BSD-3c, to be more specific.]

Signed-off-by: Davide Viti <zinosat@tiscali.it>
CC: minimod@morethan.org
CC: patrickdepinguin@gmail.com
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>