Simplify and cleanup the test for XMLHttpRequest.responseType.
Add a test for the initial value of XMLHttpRequest.responseType.
Test setting XMLHttpRequest.responseType for all readyStates.
Test setting XMLHttpRequest.responseType on a synchronous XMLHttpRequest.
Add pointers to related tests.
Merge pull request #1045 from Ms2ger/responsetype

Add more tests for XMLHttpRequest.responseType; r=hallvors