Upgrade gflags to master

Merge commit 'cb7bb2b58469b0ba5132fbcf4893b2ca76dead1c' into master

Change-Id: Id6b07c15b3bef794984d6f326d6596f043d1dde5
diff --git a/y2018/control_loops/python/2d_plot.cc b/y2018/control_loops/python/2d_plot.cc
index 52b8b34..9fb1a35 100644
--- a/y2018/control_loops/python/2d_plot.cc
+++ b/y2018/control_loops/python/2d_plot.cc
@@ -2,7 +2,7 @@
 #include <cmath>
 #include <thread>
 
-#include "third_party/gflags/include/gflags/gflags.h"
+#include "gflags/gflags.h"
 #include "third_party/matplotlib-cpp/matplotlibcpp.h"
 
 DEFINE_double(yrange, 1.0, "+- y max");