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/DenseBase_LinSpaced.cpp b/doc/snippets/DenseBase_LinSpaced.cpp
new file mode 100644
index 0000000..8e54b17
--- /dev/null
+++ b/doc/snippets/DenseBase_LinSpaced.cpp
@@ -0,0 +1,2 @@
+cout << VectorXi::LinSpaced(4,7,10).transpose() << endl;
+cout << VectorXd::LinSpaced(5,0.0,1.0).transpose() << endl;