support sequence set for search

lib/imap.utilities.js

@@ -365,7 +365,14 @@ exports.buildSearchQuery = function(options, extensions, isOrChild) {
           searchargs += modifier + criteria + ' ' + args[0];
         break;
         default:
-          throw new Error('Unexpected search option: ' + criteria);
+          try {
+            // last hope it's a seqno set
+            // http://tools.ietf.org/html/rfc3501#section-6.4.4
+            exports.validateUIDList([criteria]);
+            searchargs += modifier + criteria;
+          } catch(e) {
+            throw new Error('Unexpected search option: ' + criteria);
+          }
       }
     }
     if (isOrChild)