Change int to Index in equalsIdentity().
This fixes compilation errors in nullary test on 64-bits machines.

test/nullary.cpp

diff --git a/test/nullary.cpp b/test/nullary.cpp
index 3a46e10..70cd30d 100644
--- a/test/nullary.cpp
+++ b/test/nullary.cpp
@@ -27,17 +27,18 @@
 template<typename MatrixType>
 bool equalsIdentity(const MatrixType& A)
 {
+  typedef typename MatrixType::Index Index;
   typedef typename MatrixType::Scalar Scalar;
   Scalar zero = static_cast<Scalar>(0);
 
   bool offDiagOK = true;
-  for (int i = 0; i < A.rows(); ++i) {
-    for (int j = i+1; j < A.cols(); ++j) {
+  for (Index i = 0; i < A.rows(); ++i) {
+    for (Index j = i+1; j < A.cols(); ++j) {
       offDiagOK = offDiagOK && (A(i,j) == zero);
     }
   }
-  for (int i = 0; i < A.rows(); ++i) {
-    for (int j = 0; j < std::min(i, A.cols()); ++j) {
+  for (Index i = 0; i < A.rows(); ++i) {
+    for (Index j = 0; j < std::min(i, A.cols()); ++j) {
       offDiagOK = offDiagOK && (A(i,j) == zero);
     }
   }