merge: remove ImapMbox

 * imap: make imap_mailbox_check aware of Mailbox
 * imap: setup a mdata struct for each mailboxes
 * imap: remove ImapMbox from imap_prepare_mailbox
 * imap: remove ImapMbox from imap_adata_find signature
 * imap: remove get_mailbox()
 * imap: remove ImapMbox from imap_fast_trash()
 * imap: remove ImapMbox from imap_ac_add()
 * imap: remove ImapMbox from imap_mbox_open()
 * imap: remove ImapMbox from imap_delete_mailbox()
 * imap: remove ImapMbox from imap_adata_find()
 * imap: remove ImapMbox from imap_append_message()
 * imap: remove ImapMbox from imap_copy_messages()
 * imap: remove ImapMbox from imap_hcache_open()
 * imap: remove ImapMbox from imap_browse()
 * imap: remove useless allocation in imap_mailbox_create()
 * imap: create mdata in imap_prepare_mailbox()
 * imap: remove ImapMbox from cmd_parse_status()
 * imap: remove ImapMbox from add_folder()
 * imap: remove ImapMbox from browse_add_list_result()
 * imap: remove ImapMbox from imap_pretty_mailbox()
 * imap: remove ImapMbox and imap_parse_path()
 * imap: remove now useless param of imap_prepare_mailbox
 * imap: remove imap_parse_path2() from imap_hcache_open()
 * imap: remove imap_parse_path2() from imap_rename_mailbox()
 * imap: remove imap_parse_path2() from imap_append_message()
 * imap: always parse account in imap_parse_path2()
 * imap: remove old PINE url format
 * imap: handle all mailbox name with ImapMailboxData struct
 * imap: ensure account flags are zero'ed
 * imap: Check m->has_new to increase MailboxCount
 * imap: rename imap_parse_path2() imap_parse_path()
 * imap: rename imap_qualify_path2() to imap_qualify_path()
 * imap: rename ImapMailboxData to ImapMboxData