Update Eigen to the latest stable release, 3.2.2

./Eigen/src/Core/util/NonMPL2.h is left untouched, so that
usage of non MPL2 code is disabled.

Change-Id: I86fc9257b3c30d0ca15b268d4ef07bf038bba7ca
diff --git a/lapack/lu.cpp b/lapack/lu.cpp
index 3115116..90cebe0 100644
--- a/lapack/lu.cpp
+++ b/lapack/lu.cpp
@@ -28,8 +28,8 @@
 
   Scalar* a = reinterpret_cast<Scalar*>(pa);
   int nb_transpositions;
-  int ret = Eigen::internal::partial_lu_impl<Scalar,ColMajor,int>
-                 ::blocked_lu(*m, *n, a, *lda, ipiv, nb_transpositions);
+  int ret = int(Eigen::internal::partial_lu_impl<Scalar,ColMajor,int>
+                     ::blocked_lu(*m, *n, a, *lda, ipiv, nb_transpositions));
 
   for(int i=0; i<std::min(*m,*n); ++i)
     ipiv[i]++;