Make jQuery work without warnings in strict mode, in Firefox.

src/event/event.js

@@ -196,14 +196,14 @@ jQuery.event = {
 		event.preventDefault = function() {
 			// if preventDefault exists run it on the original event
 			if (originalEvent.preventDefault)
-				return originalEvent.preventDefault();
+				originalEvent.preventDefault();
 			// otherwise set the returnValue property of the original event to false (IE)
 			originalEvent.returnValue = false;
 		};
 		event.stopPropagation = function() {
 			// if stopPropagation exists run it on the original event
 			if (originalEvent.stopPropagation)
-				return originalEvent.stopPropagation();
+				originalEvent.stopPropagation();
 			// otherwise set the cancelBubble property of the original event to true (IE)
 			originalEvent.cancelBubble = true;
 		};

src/fx/fx.js

@@ -340,6 +340,9 @@ jQuery.fn.extend({
 				else
 					e[ val == "toggle" ? hidden ? "show" : "hide" : val ]( prop );
 			});
+
+			// For JS strict compliance
+			return true;
 		});
 	},