message: simplify: Fix a typo in math
  Also fix compilation warning for MSVC
diff: namespace meshopt
  {
  +#ifdef _MSC_VER
  +#pragma warning(disable: 4127) // conditional expression is constant; TODO remove this when kPreventFlips stops being int
  +#endif
  +
  // 0: don't prevent flips
  // 1: prevent flips by discarding edges during collapse
  // 2: prevent flips by penalizing edges that flip (single direction)
  @@ -654,8 +658,8 @@ static void fillEdgeQuadrics(Quadric* vertex_quadrics, const unsigned int* indic
  bool hasTriangleFlip(const Vector3& a, const Vector3& b, const Vector3& c, const Vector3& d)
  {
  Vector3 eb = {b.x - a.x, b.y - a.y, b.z - a.z};
  - Vector3 ec = {c.x - a.x, c.y - a.y, c.z - b.z};
  - Vector3 ed = {d.x - a.x, d.y - a.y, d.z - d.z};
  + Vector3 ec = {c.x - a.x, c.y - a.y, c.z - a.z};
  + Vector3 ed = {d.x - a.x, d.y - a.y, d.z - a.z};
  Vector3 nbc = {eb.y * ec.z - eb.z * ec.y, eb.z * ec.x - eb.x * ec.z, eb.x * ec.y - eb.y * ec.x};
  Vector3 nbd = {eb.y * ed.z - eb.z * ed.y, eb.z * ed.x - eb.x * ed.z, eb.x * ed.y - eb.y * ed.x};
  