Check thread safety in XmlHttpRequest, mostly important in Khtml

Test relates to both dojo.io.bind and dojo.hostenv.getText as it is the combination of these that is causing the browser hang.

		Propose of this test is to test for thread safety in XHR
		The problem is if you start 2 async requests, and the content of one
		these start a sync request, this sync request can be interupted
		by the other async request. That hangs the browser indefinetly.
		It should wait with the async callback until the sync exits