Combine consecutive assignments to the same value

```js
!function() {
this.foo = null;
this.bar = null;
this.baz = null;
}()
```

becomes:
```js
!function(){this.foo=null,this.bar=null,this.baz=null}();
```

but could be shortened to:
```js
!function(){this.foo=this.bar=this.baz=null}();
```