Improve benchmarking tool, add a few math benchmarks.

Change-Id: I641305dd0e4ac0705381e735ed1604c5be7aa536
diff --git a/tests/benchmark.h b/tests/benchmark.h
index 70d4c63..d7af50f 100644
--- a/tests/benchmark.h
+++ b/tests/benchmark.h
@@ -32,6 +32,8 @@
 
   Benchmark* Arg(int x);
 
+  const char* Name();
+
   bool ShouldRun(int argc, char* argv[]);
   void Run();