Several compilation fixes for MSVC and NVCC, basically:

- added explicit enum to int conversion where needed
- if a function is not defined as declared and the return type is "tricky"
  then the type must be typedefined somewhere. A "tricky return type" can be:
  * a template class with a default parameter which depends on another template parameter
  * a nested template class, or type of a nested template class

Eigen/src/QR/QR.h

@@ -168,7 +168,7 @@ MatrixType QR<MatrixType>::matrixQ(void) const
   * \sa class QR
   */
 template<typename Derived>
-const QR<typename ei_eval<Derived>::type>
+const QR<typename MatrixBase<Derived>::EvalType>
 MatrixBase<Derived>::qr() const
 {
   return QR<typename ei_eval<Derived>::type>(derived());

Eigen/src/QR/SelfAdjointEigenSolver.h

@@ -41,6 +41,7 @@ template<typename _MatrixType> class SelfAdjointEigenSolver
 {
   public:
 
+    enum {Size = _MatrixType::RowsAtCompileTime };
     typedef _MatrixType MatrixType;
     typedef typename MatrixType::Scalar Scalar;
     typedef typename NumTraits<Scalar>::Real RealScalar;
@@ -49,6 +50,18 @@ template<typename _MatrixType> class SelfAdjointEigenSolver
     typedef Matrix<RealScalar, Dynamic, 1> RealVectorTypeX;
     typedef Tridiagonalization<MatrixType> TridiagonalizationType;
 
+    SelfAdjointEigenSolver()
+        : m_eivec(Size, Size),
+          m_eivalues(Size)
+    {
+      ei_assert(Size!=Dynamic);
+    }
+
+    SelfAdjointEigenSolver(int size)
+        : m_eivec(size, size),
+          m_eivalues(size)
+    {}
+
     /** Constructors computing the eigenvalues of the selfadjoint matrix \a matrix,
       * as well as the eigenvectors if \a computeEigenvectors is true.
       *