identity: Add new identity driver

identity: Add new identity driver

	This driver does no transformation of the gallium calls
	going to the real driver, like the identity matrix. It is
	intended to be the basis for transforming and/or debug
	drivers like trace and rbug.

	Authors of this patch are:
		Michal Krol, orignal heavy lifting.
		José Fonesca, object wrapping code stolen from trace.
		Jakob Bornecrantz, put it all toghether and renamed a stuff.