Merge branch 'master' into lesserphp

* master: (70 commits)
  Release preparation
  translation update
  do not disclose email or IP addresses of users through RSS
  small fix
  Make default encapsulation more readable and less duplicate.
  Replace htmlspecialchars to hsc in core
  Add the preview-bool for the cache file.
  Add htmlspecialchars when showing $DATE_AT
  #2021 broken links to W3C validators also dokuwiki and php are on https
  made bin/wantedpage.php more flexible
  doc abbreviation
  Fix PHP Notices: Reduce error log noise
  Create valid empty options
  translation update
  doc fix
  translation update
  using $options->getCmd to retrieve show-pages parameter
  added option to wantedpages.php to show or not show pages where broken links occur
  show pages where broken links occur: page_id => broken_link
  clean extension names. fixes #2042
  ...