mesa3d-demos: new package

[Thomas:
 - add license information, even if there's unfortunately no license
   file
 - rename patches to use the correct convention.]

Signed-off-by: Spenser Gilliland <spenser@gillilanding.com>
Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>