libdri2: new package

libdri2 is a library for the DRI2 extension to the X Window System. This
is the split out dri2 client side code from mesa, libva, libvdpau, etc..

It can be used by applications or user-space drivers to provide
accelerated graphics.

Signed-off-by: Jérôme Oufella <jerome.oufella@savoirfairelinux.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>