Fix Camera culling bugs (Issue phaserjs#4092)

Make camera culling properly handle the camera's current zoom level and viewport position.

Author: cirras

src/cameras/2d/BaseCamera.js

@@ -727,11 +727,12 @@ var BaseCamera = new Class({
             var ty = (objectX * mvb + objectY * mvd + mvf);
             var tw = ((objectX + objectW) * mva + (objectY + objectH) * mvc + mve);
             var th = ((objectX + objectW) * mvb + (objectY + objectH) * mvd + mvf);
-            var cullW = cameraW + objectW;
-            var cullH = cameraH + objectH;
+            var cullTop = this.y;
+            var cullBottom = cullTop + cameraH;
+            var cullLeft = this.x;
+            var cullRight = cullLeft + cameraW;
 
-            if (tx > -objectW && ty > -objectH && tx < cullW && ty < cullH &&
-                tw > -objectW && th > -objectH && tw < cullW && th < cullH)
+            if ((tw > cullLeft && tx < cullRight) && (th > cullTop && ty < cullBottom))
             {
                 culledObjects.push(object);
             }