Enable drop bug workaround for IE11 and up

Another bug that is carried on from ie10 to ie11.

Closes #2476

Author: marijnh

lib/codemirror.js

@@ -2781,7 +2781,7 @@
     if (signalDOMEvent(cm, e) || eventInWidget(cm.display, e))
       return;
     e_preventDefault(e);
-    if (ie_upto10) lastDrop = +new Date;
+    if (ie) lastDrop = +new Date;
     var pos = posFromMouse(cm, e, true), files = e.dataTransfer.files;
     if (!pos || isReadOnly(cm)) return;
     // Might be a file drop, in which case we simply extract the text
@@ -2826,7 +2826,7 @@
   }
 
   function onDragStart(cm, e) {
-    if (ie_upto10 && (!cm.state.draggingText || +new Date - lastDrop < 100)) { e_stop(e); return; }
+    if (ie && (!cm.state.draggingText || +new Date - lastDrop < 100)) { e_stop(e); return; }
     if (signalDOMEvent(cm, e) || eventInWidget(cm.display, e)) return;
 
     e.dataTransfer.setData("Text", cm.getSelection());