(erase_dir_iff_empty): optimization.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(my_mkdir_rec): ret rid of double directory name conversion.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(my_mkdir): don't call mc_mkdir() twice in case of failure.

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