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/MatrixBase_all.cpp b/doc/snippets/MatrixBase_all.cpp
new file mode 100644
index 0000000..46f26f1
--- /dev/null
+++ b/doc/snippets/MatrixBase_all.cpp
@@ -0,0 +1,7 @@
+Vector3f boxMin(Vector3f::Zero()), boxMax(Vector3f::Ones());
+Vector3f p0 = Vector3f::Random(), p1 = Vector3f::Random().cwiseAbs();
+// let's check if p0 and p1 are inside the axis aligned box defined by the corners boxMin,boxMax:
+cout << "Is (" << p0.transpose() << ") inside the box: "
+     << ((boxMin.array()<p0.array()).all() && (boxMax.array()>p0.array()).all()) << endl;
+cout << "Is (" << p1.transpose() << ") inside the box: "
+     << ((boxMin.array()<p1.array()).all() && (boxMax.array()>p1.array()).all()) << endl;