Latest Mesa Update Lands In Ubuntu 16.04, Enables OpenGL 4.1 With LLVM 3.8

In the process of landing in the Ubuntu 16.04 "Xenial Xerus" package archive is the newly-minted Mesa 11.1.2. While a point release update for Ubuntu of Mesa isn't usually noteworthy, with this change they are also building against LLVM 3.8 to allow OpenGL 4.1 support for the RadeonSI Gallium3D driver...