chore(IE8): remove all IE8 specific code

Remove all code that was IE8 specific
>
> Tell me one browser that doesn't have XMLHttpRequest
>
IE (all versions) has an auto-destruct mode called (as a disguise) "Disable
native XMLHttpRequest". Only the ActiveX one remains available then.

With such a setting everything must be so broken, though, that I'm not sure
if this message adds any new info to such users. ;)