Fix backup handling and restoring file modes of existing directories

Fix backup handling and restoring file modes of existing directories

* NEWS, THANKS: Update
* src/extract.c (extract_dir): reset status to 0 if the
directory already exists.
* src/misc.c (maybe_backup_file): Assign before_backup_name
and clear after_backup_name before checking if we really need
to backup the file.
* tests/backup01.at: New testcase.
* tests/extrac08.at: New testcase.
* tests/Makefile.am, tests/testsuite.at: Add extrac08.at and
backup01.at