Fix weekly cronjob

[mrlnc]

cron.weekly is implemented using run-parts, which just runs any executable in a directory. Haha, no, executables must not have any dot in their name.

Besides, making sure that the script isn't writable for non-root users (wouldn't execute then, either).

[CoRfr]

Oh so the weekly jobs were not running all that time ... oh well, thanks for fixing that!