Make shift-ctrl-click extend the primary selection

Issue #2478

Author: marijnh

lib/codemirror.js

@@ -2613,7 +2613,7 @@
     e_preventDefault(e);
 
     var ourRange, ourIndex, startSel = doc.sel;
-    if (addNew) {
+    if (addNew && !e.shiftKey) {
       ourIndex = doc.sel.contains(start);
       if (ourIndex > -1)
         ourRange = doc.sel.ranges[ourIndex];