(recursive_erase): ret rid of extra path conversion.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(erase_dir_iff_empty): get rid of extra directory name conversion.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(copy_dir_dir): ret rid of extra memory allocation.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(move_dir_dir): ret rid of extra memory allocation.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>