fix for ubsan on unittest.h fastrand()

unit_test/unit_test.h

Index: unit_test/unit_test.h
diff --git a/unit_test/unit_test.h b/unit_test/unit_test.h
index f816ec711ac4dc51be3937ff832f0faaf39840e0..8e600e15e7e28d362451d45321e0510f99f8119f 100644
--- a/unit_test/unit_test.h
+++ b/unit_test/unit_test.h
@@ -57,7 +57,8 @@ static inline double get_time() {
 
 extern int fastrand_seed;

[pbos-webrtc, 2016/02/02 21:11:47]

Just use an unsigned int, then fastrand_seed >> 16 % 0xFFFFu casts to an int
without overflows.

[fbarchard1, 2016/02/02 22:23:33]

Done.

 inline int fastrand() {
-  fastrand_seed = fastrand_seed * 214013 + 2531011;
+  fastrand_seed = static_cast<int>(
+      static_cast<unsigned int>(fastrand_seed) * 214013u + 2531011u);
   return (fastrand_seed >> 16) & 0xffff;
 }