Fix an issue with the cursor sometimes disappearing when a patch was received

Update CodeMirror to the latest version (5.13.2)

www/code/codemirror-5.13.2/test/lint.js

@@ -0,0 +1,11 @@
+var blint = require("blint");
+
+["mode", "lib", "addon", "keymap"].forEach(function(dir) {
+  blint.checkDir(dir, {
+    browser: true,
+    allowedGlobals: ["CodeMirror", "define", "test", "requirejs"],
+    blob: "// CodeMirror, copyright (c) by Marijn Haverbeke and others\n// Distributed under an MIT license: http:\/\/codemirror.net\/LICENSE\n\n"
+  });
+});
+
+module.exports = {ok: blint.success()};