Added flag UNSEEN in Zend_Mail_Storage

Closes #532

library/Zend/Mail/Storage.php

@@ -31,6 +31,7 @@ class Zend_Mail_Storage
     // system flags and other flags
     const FLAG_PASSED   = 'Passed';
     const FLAG_SEEN     = '\Seen';
+    const FLAG_UNSEEN   = '\Unseen';
     const FLAG_ANSWERED = '\Answered';
     const FLAG_FLAGGED  = '\Flagged';
     const FLAG_DELETED  = '\Deleted';

library/Zend/Mail/Storage/Imap.php

@@ -88,6 +88,7 @@ class Zend_Mail_Storage_Imap extends Zend_Mail_Storage_Abstract
     protected static $_knownFlags = array('\Passed'   => Zend_Mail_Storage::FLAG_PASSED,
                                           '\Answered' => Zend_Mail_Storage::FLAG_ANSWERED,
                                           '\Seen'     => Zend_Mail_Storage::FLAG_SEEN,
+                                          '\Unseen'   => Zend_Mail_Storage::FLAG_UNSEEN,
                                           '\Deleted'  => Zend_Mail_Storage::FLAG_DELETED,
                                           '\Draft'    => Zend_Mail_Storage::FLAG_DRAFT,
                                           '\Flagged'  => Zend_Mail_Storage::FLAG_FLAGGED);
@@ -99,6 +100,7 @@ class Zend_Mail_Storage_Imap extends Zend_Mail_Storage_Abstract
     protected static $_searchFlags = array('\Recent'   => 'RECENT',
                                            '\Answered' => 'ANSWERED',
                                            '\Seen'     => 'SEEN',
+                                           '\Unseen'   => 'UNSEEN',
                                            '\Deleted'  => 'DELETED',
                                            '\Draft'    => 'DRAFT',
                                            '\Flagged'  => 'FLAGGED');