Introduce local variable to track directory change
Change snprintf to copy_str in change_directory()
Fix overwrite of previously visited directory

On changing to the current directory. It made `:cd -` and ''
useless after, for instance, switching panes.
Make marks definition more concrete
Document special bookmarks

'', '< and '>.
Fix error message on navigating to wrong bookmark

Wasn't displayed.
Better treating of special bookmarks
Merge branch 'do-not-update-last-dir-on-reloading'

Fix overwrite of previously visited directory on view update (made
`:cd -` and '' useless after, for instance, switching panes).

Fix error message on navigating to a wrong bookmark.