Added support for matrix exponential to Eigen

Change-Id: I7ba752ed3250e7803880cbe40794cc1b26bacf32
diff --git a/third_party/eigen/BUILD b/third_party/eigen/BUILD
index 7012271..3f4fc4c 100644
--- a/third_party/eigen/BUILD
+++ b/third_party/eigen/BUILD
@@ -14,5 +14,6 @@
     'Eigen/SPQRSupport',
     'Eigen/SuperLUSupport',
     'Eigen/UmfPackSupport',
-  ]),
+  ]) + ['unsupported/Eigen/MatrixFunctions'] +
+  glob(['unsupported/Eigen/src/MatrixFunctions/*.h']),
 )