message: Don't use GLEW with OpenGLES
diff: @@ -18,7 +18,9 @@ std::string gl::last_error()
  GLenum err = glGetError();
  if (err != GL_NO_ERROR)
  {
  +#if VSNRAY_HAVE_GLEW
  return std::string(reinterpret_cast<char const*>(glewGetErrorString(err)));
  +#endif
  }
  return "";
  }
  