fix($http): update httpBackend to use ActiveXObject on IE8 if necessary

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 #5677
Closes #5679

docs/content/error/httpBackend/noxhr.ngdoc

@@ -0,0 +1,10 @@
+@ngdoc error
+@name $httpBackend:noxhr
+@fullName Unsupported XHR
+@description
+
+This error occurs in browsers that do not support XmlHttpRequest. AngularJS
+supports Safari, Chrome, Firefox, Opera, IE8 and higher, and mobile browsers
+(Android, Chrome Mobile, iOS Safari). To avoid this error, use an officially
+supported browser.
+

src/ng/httpBackend.js

@@ -1,13 +1,18 @@
 'use strict';
 
 function createXhr(method) {
-  // IE8 doesn't support PATCH method, but the ActiveX object does
-  /* global ActiveXObject */
-  return (msie <= 8 && lowercase(method) === 'patch')
-      ? new ActiveXObject('Microsoft.XMLHTTP')
-      : new window.XMLHttpRequest();
-}
+    //if IE and the method is not RFC2616 compliant, or if XMLHttpRequest
+    //is not available, try getting an ActiveXObject. Otherwise, use XMLHttpRequest
+    //if it is available
+    if (msie <= 8 && (!method.match(/^(get|post|head|put|delete|options)$/i) ||
+      !window.XMLHttpRequest)) {
+      return new ActiveXObject("Microsoft.XMLHTTP");
+    } else if (window.XMLHttpRequest) {
+      return new window.XMLHttpRequest();
+    }
 
+    throw minErr('$httpBackend')('noxhr', "This browser does not support XMLHttpRequest.");
+}
 
 /**
  * @ngdoc object