Squashed 'third_party/eigen/' content from commit 61d72f6

Change-Id: Iccc90fa0b55ab44037f018046d2fcffd90d9d025
git-subtree-dir: third_party/eigen
git-subtree-split: 61d72f6383cfa842868c53e30e087b0258177257
diff --git a/doc/snippets/Map_inner_stride.cpp b/doc/snippets/Map_inner_stride.cpp
new file mode 100644
index 0000000..d95ae9b
--- /dev/null
+++ b/doc/snippets/Map_inner_stride.cpp
@@ -0,0 +1,5 @@
+int array[12];
+for(int i = 0; i < 12; ++i) array[i] = i;
+cout << Map<VectorXi, 0, InnerStride<2> >
+         (array, 6) // the inner stride has already been passed as template parameter
+     << endl;