function clone(a) {
  var out = new glMatrix.ARRAY_TYPE(4);
  out[0] = a[0];
  out[1] = a[1];
  out[2] = a[2];
  out[3] = a[3];
  return out;
}
Creates a new vec4 initialized with values from an existing vector

@param {vec4} a vector to clone
@returns {vec4} a new 4D vector