Backward Compatibility Breaking Horde Issues (aka Horde 4.0 TODO)

• Fix cloning behavior (See Bug 1410).
  • Remove deprecated code in IMAP_Tree::.
  • Move IMP_IMAPClient:: to Horde.
  • Merge IMP_Thread:: to IMAP_Thread::.
  • Encrypt deprecations in Horde_Crypt_pgp::.
  • Use one place for clear text sendmail error messages.