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_applyOnTheLeft.cpp b/doc/snippets/MatrixBase_applyOnTheLeft.cpp
new file mode 100644
index 0000000..6398c87
--- /dev/null
+++ b/doc/snippets/MatrixBase_applyOnTheLeft.cpp
@@ -0,0 +1,7 @@
+Matrix3f A = Matrix3f::Random(3,3), B;
+B << 0,1,0,  
+     0,0,1,  
+     1,0,0;
+cout << "At start, A = " << endl << A << endl;
+A.applyOnTheLeft(B); 
+cout << "After applyOnTheLeft, A = " << endl << A << endl;