Fix simple-mode unicode regex flag being dropped

Author: infime

mode/simple-mode.js

@@ -37,6 +37,7 @@ function toRegex(val, caret) {
   var flags = "";
   if (val instanceof RegExp) {
     if (val.ignoreCase) flags = "i";
+    if (val.unicode) flags += "u";
     val = val.source;
   } else {
     val = String(val);