Fix calling methods on new objects (e.g. (new foo())->doSomething()).

Fixes #86.

tested on the code from that issue:
```php
<?php

class :span {}

class foo {
    public function doSomething()
    {
    }
}

$bar = <span></span>;    // without this line, the code is all good

(new foo())->doSomething();    // error

var_dump('Finished.');
```

xhpize before:
```php
<?php

class xhp_span{}

class foo{
public function doSomething()
{
}
}

$bar=new \xhp_span(array(), array(), __FILE__, 11);

(new foo()->doSomething();

var_dump('Finished.');
```
(note the missing close paren on the class instantiation).

xhpize after:
```php
<?php

class xhp_span{}

class foo{
public function doSomething()
{
}
}

$bar=new \xhp_span(array(), array(), __FILE__, 11);

(new foo())->doSomething();

var_dump('Finished.');
```