Add QR and Cholesky module instantiations in the lib.

To try it with the unit tests set the cmake variable TEST_LIB to ON.

Eigen/src/QR/QR.h

@@ -75,6 +75,8 @@ template<typename MatrixType> class QR
     VectorType m_hCoeffs;
 };
 
+#ifndef EIGEN_HIDE_HEAVY_CODE
+
 template<typename MatrixType>
 void QR<MatrixType>::_compute(const MatrixType& matrix)
 {
@@ -157,6 +159,8 @@ MatrixType QR<MatrixType>::matrixQ(void) const
   return res;
 }
 
+#endif // EIGEN_HIDE_HEAVY_CODE
+
 /** \return the QR decomposition of \c *this.
   *
   * \sa class QR