Log Message:
Changes 1.0.2:
* Added explicit copy constructors to Imath::Matrix33<T> and
  ImathMatrix44<T> to make conversions between float and double
  matrices more convenient.
* Added slerpShortestArc() and euclideanInnerProduct() functions
  to Imath::Quat<T>.
* Added 4D vector class template Imath::Vec4<T>.
* Copy constructors and assignment operators for Matrix33<T>
  and Matrix44<T> are up to 25% faster.  Added matrix constructors
  that do not initialize the matrix (this is faster in cases where
  the initial value of the matrix is immediately overwritten anyway).
* Rewrote function closestPointOnBox(point,box).  Shortened
  the code, improved numerical accuracy, fixed a bug where
  closestPointOnBox(box.center(),box) would return the center
  of the +Z side of the box, even if the +/-X or +/-Y sides
  were closer.
* Rewrote function findEntryAndExitPoints() in ImathBoxAlgo.h.
  Results are now consistent with those from intersect(), also
  in ImathBoxAlgo.h.
* Made Vec2<T>::length() and Vec3<T>::length() more accurate for
  vectors whose length is less than sqrt(limits<T>::smallest());
* Made Quat<T>::angle() more accurate for small angles.