hack to get jQuery record-replay working on phantomjs

Currently, record-replay of jQuery 2.0.2 works fine on Chrome, but not in PhantomJS.  The issue in PhantomJS is that for Safari's Webkit, `typeof XMLHttpRequest` (and various other native functions) is `object` rather than `function`.  (This behavior remains even for the most recent version of Safari.)  This leads to replay errors for scripts like:

```javascript
var xhrSupported = new XMLHttpRequest();
```

During replay, we get the error:

```
/Users/m.sridharan/git-repos/jalangi/src/js/analysis.js:703
                throw tmp;
                      ^
TypeError: object is not a function
    at callAsNativeConstructor (/Users/m.sridharan/git-repos/jalangi/src/js/analysis.js:441:24)
    at callAsConstructor (/Users/m.sridharan/git-repos/jalangi/src/js/analysis.js:463:27)
    at invokeFun (/Users/m.sridharan/git-repos/jalangi/src/js/analysis.js:525:31)
    at /Users/m.sridharan/git-repos/jalangi/src/js/analysis.js:618:24
    at Object.<anonymous> (/private/tmp/foo2_jalangi_.js:13:257)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:364:17)
```

It would be nice to have replay work for this case on PhantomJS, since then we could add tests based on recent jQuery versions to our regression suite.

The code change attached to this pull request "fixes" the problem, by special-casing the function test for XMLHttpRequest.  But, it's a total hack.  Unfortunately, I can't think of a more general way to detect and address this issue.  

Is there a better way to fix this problem?