Connection: drop restrictive flag check for addFlags()

lib/Connection.js

@@ -473,13 +473,8 @@ Connection.prototype._store = function(which, uids, flags, isAdding, cb) {
     flags = [flags];
   for (var i = 0, len = flags.length; i < len; ++i) {
     if (!isKeywords) {
-      if (flags[i][0] === '\\')
-        flags[i] = flags[i].substr(1);
-      if (this._box.permFlags.indexOf(flags[i].toLowerCase()) === -1
-          || flags[i] === '*')
-        throw new Error('The flag "' + flags[i]
-                        + '" is not allowed by the server for this mailbox');
-      flags[i] = '\\' + flags[i];
+      if (flags[i][0] !== '\\')
+        flags[i] = '\\' + flags[i];
     } else {
       // keyword contains any char except control characters (%x00-1F and %x7F)
       // and: '(', ')', '{', ' ', '%', '*', '\', '"', ']'