function round(out, a) {
  out[0] = glMatrix.round(a[0]);
  out[1] = glMatrix.round(a[1]);
  out[2] = glMatrix.round(a[2]);
  out[3] = glMatrix.round(a[3]);
  return out;
}
symmetric round the components of a vec4

@param {vec4} out the receiving vector
@param {ReadonlyVec4} a vector to round
@returns {vec4} out