add new function to mailbox_t mailbox_recent_count()

This was usefull to implement SELECT/EXAMINE for imap4

 /* GNU mailutils - a suite of utilities for electronic mail
-   Copyright (C) 1999, 2000 Free Software Foundation, Inc.
+   Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU Library General Public License as published by
@@ -69,6 +69,7 @@ struct _mailbox
   int  (*_get_message)     __P ((mailbox_t, size_t msgno, message_t *msg));
   int  (*_append_message)  __P ((mailbox_t, message_t msg));
   int  (*_messages_count)  __P ((mailbox_t, size_t *num));
+  int  (*_recent_count)    __P ((mailbox_t, size_t *num));
   int  (*_expunge)         __P ((mailbox_t));
 
   int  (*_scan)            __P ((mailbox_t, size_t msgno, size_t *count));

@@ -220,6 +220,14 @@ mailbox_messages_count (mailbox_t mbox, size_t *num)
 }
 
 int
+mailbox_recent_count (mailbox_t mbox, size_t *num)
+{
+  if (mbox && mbox->_recent_count)
+    return mbox->_recent_count (mbox, num);
+  return mailbox_messages_count (mbox, num);
+}
+
+int
 mailbox_expunge (mailbox_t mbox)
 {
   if (mbox == NULL || mbox->_expunge == NULL)

@@ -122,6 +122,7 @@ static int mbox_close                 __P ((mailbox_t));
 static int mbox_get_message           __P ((mailbox_t, size_t, message_t *));
 static int mbox_append_message        __P ((mailbox_t, message_t));
 static int mbox_messages_count        __P ((mailbox_t, size_t *));
+static int mbox_recent_count          __P ((mailbox_t, size_t *));
 static int mbox_expunge               __P ((mailbox_t));
 static int mbox_scan                  __P ((mailbox_t, size_t, size_t *));
 static int mbox_is_updated            __P ((mailbox_t));
@@ -209,6 +210,7 @@ _mailbox_mbox_init (mailbox_t mailbox)
   mailbox->_get_message = mbox_get_message;
   mailbox->_append_message = mbox_append_message;
   mailbox->_messages_count = mbox_messages_count;
+  mailbox->_recent_count = mbox_recent_count;
   mailbox->_expunge = mbox_expunge;
 
   mailbox->_scan = mbox_scan;
@@ -1534,6 +1536,25 @@ mbox_messages_count (mailbox_t mailbox, size_t *pcount)
   return 0;
 }
 
+static int
+mbox_recent_count (mailbox_t mailbox, size_t *pcount)
+{
+  mbox_data_t mud = mailbox->data;
+  mbox_message_t mum;
+  size_t j, total;
+
+  if (pcount)
+    return EINVAL;
+  for (total = j = 0; j < mud->messages_count; j++)
+    {
+      mum = mud->umessages[j];
+      if (mum && mum->new_flags == 0)
+	total++;
+    }
+  *pcount = total;
+  return 0;
+}
+
 #ifdef WITH_PTHREAD
 static void
 mbox_cleanup (void *arg)