- Added the ANGLE extension for instance
  drawing (GL_ANGLE_instanced_arrays)
- VertexDataManager can now pull data
  either from the current attributes
  or from the VertexArray object

Change-Id: Id0aa078bf9401e4f3f62594e90908fad98954051
Reviewed-on: https://swiftshader-review.googlesource.com/2946Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>