window.XMLHttpRequest is not always available in IE8 despite it not running in quirks mode,
in which case Angular should be using the ActiveXObject instead. Just checking the browser
version is taking too many shortcuts.
Closes#5677Closes#5679
IE8's native XHR doesn't support PATCH requests, but the ActiveX one does.
I'm also removing the noxhr error doc because nobody will ever get that error.
Closes#2518Closes#5043