shaders: Add glmark2(-es2) shaders
glmark2 is a popular OpenGL (2.1 / ES 2.0) benchmark on Linux. Let's add its shaders. The shaders are licensed under the GPLv3 (https://github.com/glmark2/glmark2/blob/master/COPYING)
Signed-off-by: Alyssa Rosenzweig alyssa.rosenzweig@collabora.com