Add small chrono timer object

This is just so if someone wants a quick way to measure how long
something takes for benchmarking purposes they don't have to
reinvent anything. See examples in comments

common/timer.h

@@ -19,6 +19,7 @@
 #define TIMER_H
 
 #include "types.h"
+#include <chrono>
 
 // Disgrace: for windows compile
 #ifdef _WINDOWS
@@ -65,4 +66,28 @@ private:
 	bool	pUseAcurateTiming;
 };
 
+/* Wrapper around chrono to make adding simple time based benching easy
+ * ex:
+ * void foo() {
+ * ...
+ * BenchTimer timer;
+ * ... (expensive work here)
+ * auto dur = timer.elapsed();
+ * std::cout << "foo() took " << dur << seconds" << std::endl;
+ * ...
+ * }
+ * */
+
+struct BenchTimer
+{
+	typedef std::chrono::high_resolution_clock clock;
+
+	BenchTimer() : start_time(clock::now()) {}
+	void reset() { start_time = clock::now(); }
+	// this is seconds
+	double elapsed() { return std::chrono::duration<double> (clock::now() - start_time).count(); }
+private:
+	std::chrono::time_point<std::chrono::high_resolution_clock> start_time;
+};
+
 #endif