added this.cancel() for canceling events inside an event handling function.

build.xml

@@ -58,6 +58,7 @@
 
   <target name="get-canary" depends="init" description="Downloads canarymod jar" unless="canary.present">
     <get src="https://ci.visualillusionsent.net/job/CanaryMod/lastStableBuild/artifact/*zip*/archive.zip"
+	 maxtime="60"
 	 dest="target/canarymod.zip"
 	 verbose="true"/>
     <unzip src="target/canarymod.zip"

src/main/js/lib/events-bukkit.js

@@ -49,7 +49,16 @@ exports.on = function(
           evt.setCancelled(true);
         }
       }
-      handler.call( result, evt, cancel );
+      /*
+       let handlers use this.cancel() to cancel the current event
+       or this.unregister() to unregister from future events.
+       */
+      var bound = {};
+      for (var i in result){
+        bound[i] = result[i];
+      }
+      bound.cancel = cancel;
+      handler.call( bound, evt, cancel );
     } 
   } );
   /* 

src/main/js/lib/events-canary.js

@@ -30,8 +30,17 @@ exports.on = function(
         e.setCanceled();
       }
     }
+    /*
+     let handlers use this.cancel() to cancel the current event
+     or this.unregister() to unregister from future events.
+     */
+    var bound = {};
+    for (var i in result){
+      bound[i] = result[i];
+    }
+    bound.cancel = cancel;
     try { 
-      handler.call(result, e, cancel); 
+      handler.call(bound, e, cancel); 
     } catch ( error ){
       console.log('Error while executing handler:' + handler + 
                   ' for event type:' + eventType + 

src/main/js/lib/events.js

@@ -74,9 +74,11 @@ events.on( Packages.net.canarymod.hook.player.BlockDestroyHook, function( evt, c
 ```
 
 The `this` keyword when used inside the callback function refers to
-the Listener object created by ScriptCraft. It has a single method
-`unregister()` which can be used to stop listening. This is the same
-object which is returned by the `events.on()` function.
+the Listener object created by ScriptCraft. It has 2 methods
+`unregister()` which can be used to stop listening and `cancel()`
+which can be used to cancel the current event. The object returned by
+`events.on()` only has the `unregister()` method, the `cancel()`
+method is only available from within the event handling function.
 
 To unregister a listener *outside* of the listener function...