Copy codemirror mode configuration instead of changing it

If we change it, the modified (wrong) mode is saved in the notebook, which
wrecks havoc on highlighting once the notebook is saved and reopened.

IPython/html/static/notebook/js/codemirror-ipython.js

@@ -1,17 +1,22
 // IPython mode is just a slightly altered Python Mode with `?` beeing a extra
 // single operator. Here we define `ipython` mode in the require `python`
 // callback to auto-load python mode, which is more likely not the best things
 // to do, but at least the simple one for now.
 
 CodeMirror.requireMode('python',function(){
     "use strict";
 
     CodeMirror.defineMode("ipython", function(conf, parserConf) {
-
-        parserConf.singleOperators = new RegExp("^[\\+\\-\\*/%&|\\^~<>!\\?]");
-        parserConf.name = 'python'
-        return CodeMirror.getMode(conf, parserConf);
+        var pythonConf = {};
+        for (var prop in parserConf) {
+            if (parserConf.hasOwnProperty(prop)) {
+                pythonConf[prop] = parserConf[prop];
+            }
+        }
+        pythonConf.name = 'python';
+        pythonConf.singleOperators = new RegExp("^[\\+\\-\\*/%&|\\^~<>!\\?]");
+        return CodeMirror.getMode(conf, pythonConf);
     }, 'python');
 
     CodeMirror.defineMIME("text/x-ipython", "ipython");
 })