Use regexs when matching for ignored_folders.
  `maildirs_matching` now uses regexs, not substrings.
  The "/" operation now uses regexps.

  That is the scroll_index_to and scroll_message_to use regexps
 internally, not substrings.
  Fixed typo:  "-prot" -> "t-prot".
  Fixed bogus brace-placement.