Merge branch '2877_stable_cleanup' into 4.8.1-stable

Merge branch '2877_stable_cleanup' into 4.8.1-stable

* 2877_stable_cleanup:
  Update EN and RU man pages: add missing options.
  fixed doxygen.cfg, excluded directory /tests/ from doxygen path's
  Ticket #2861: additional error handling in edit_save_block().
  (str_utf8_normalize): ret rid of extra memory allocation.
  Use g_strndup() instead of g_strdup()
  (get_absolute_name): missing finish NULL in vfs_path_append_vpath_new() call.
  (edit_do_undo): cleanup of labeled statement usage.
  mcdiffview: code cleanup and cosmetics.
  Cleanup of screen library detection m4 code.
  Refactoring of many conditions.
  (edit_do_search): refactoring of search loop condition.
  Avoid double checks of bookmarks in editor.
  Ticket #2877: code cleanup before 4.8.1.6 release.