Add timestamp support.

scripts/speed_test.rhai

@@ -1,6 +1,7 @@
 // This script runs 1 million iterations
 // to test the speed of the scripting engine.
 
+let now = timestamp();
 let x = 1_000_000;
 
 print("Ready... Go!");
@@ -9,4 +10,4 @@ while x > 0 {
     x = x - 1;
 }
 
-print("Finished.");
+print("Finished. Run time = " + now.elapsed() + " seconds.");