Create an OpenGL ES 2.0 context and verify the renderer string. This
ensures the expected libGLESv2 get loaded and initialized correctly.
Also add unittests to the Visual Studio solution.

Change-Id: I848079215434ce1fb9a18564ce47de5b598b21d2
Reviewed-on: https://swiftshader-review.googlesource.com/10108Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>