[GR-4450] Report “FastR” as scripting engine.

com.oracle.truffle.r.engine/src/com/oracle/truffle/r/engine/shell/RscriptCommand.java

@@ -124,7 +124,7 @@ public class RscriptCommand {
 
     private static void printVersionAndExit() {
         // TODO Not ok in nested context
-        System.out.print("R scripting front-end version ");
+        System.out.print("FastR scripting front-end version ");
         System.out.println(RVersionNumber.FULL);
         System.exit(0);
     }