Squashed 'third_party/eigen/' changes from 61d72f6..cf794d3


Change-Id: I9b814151b01f49af6337a8605d0c42a3a1ed4c72
git-subtree-dir: third_party/eigen
git-subtree-split: cf794d3b741a6278df169e58461f8529f43bce5d
diff --git a/doc/snippets/Tutorial_ReshapeMat2Vec.cpp b/doc/snippets/Tutorial_ReshapeMat2Vec.cpp
new file mode 100644
index 0000000..95bd4e0
--- /dev/null
+++ b/doc/snippets/Tutorial_ReshapeMat2Vec.cpp
@@ -0,0 +1,11 @@
+MatrixXf M1(3,3);    // Column-major storage
+M1 << 1, 2, 3,
+      4, 5, 6,
+      7, 8, 9;
+
+Map<RowVectorXf> v1(M1.data(), M1.size());
+cout << "v1:" << endl << v1 << endl;
+
+Matrix<float,Dynamic,Dynamic,RowMajor> M2(M1);
+Map<RowVectorXf> v2(M2.data(), M2.size());
+cout << "v2:" << endl << v2 << endl;
\ No newline at end of file