uprev Virglrenderer in Mesa

It's practical to have the brother uprev of the uprev_Mesa_in_virglrenderer. When this currently working uprev has trouble, it is useful to see if the problems are also on the other front.

But it also has value by itself. It is one of the Mesa dependencies that, sporadically, developers like to see a recent version.

It has a "Cons" as this uprev is seen often in Mesa, together with the crosvm uprev. It is in the same file where those two dependencies are established the release to use.