* LU decomposition, supporting all rectangular matrices, with full

pivoting for better numerical stability. For now the only application is
determinant.
* New determinant unit-test.
* Disable most of Swap.h for now as it makes LU fail (mysterious).
Anyway Swap needs a big overhaul as proposed on IRC.
* Remnants of old class Inverse removed.
* Some warnings fixed.

Eigen/src/QR/QR.h

@@ -171,7 +171,7 @@ template<typename Derived>
 const QR<typename MatrixBase<Derived>::EvalType>
 MatrixBase<Derived>::qr() const
 {
-  return QR<typename ei_eval<Derived>::type>(derived());
+  return eval();
 }