function getTranslation(m, dst) {
  dst = dst || v3.create();
  dst[0] = m[12];
  dst[1] = m[13];
  dst[2] = m[14];
  return dst;
}
Returns the translation component of a 4-by-4 matrix as a vector with 3
entries.
@param {module:twgl/m4.Mat4} m The matrix.
@param {module:twgl/v3.Vec3} [dst] vector to hold result. If not passed a new one is created.
@return {module:twgl/v3.Vec3} The translation component of m.
@memberOf module:twgl/m4