trash-empty: remove files without write bit

[curious-rabbit]

A directory in the trash can lack its write bit. Removing a directory needs the write bit to delete the entries inside it, so trash-empty stopped with "cannot remove" and left the directory, although the user owns it.

trash-empty now adds the write and search bits to the directories it owns before removing them. A directory that cannot even be listed (no read bit) is still left in place and reported.

$ trash-put ~/project
$ chmod -w ~/.local/share/Trash/files/project
$ trash-empty
trash-empty: cannot remove /home/user/.local/share/Trash/files/project