Fix for password-protected .rar files

[Denis Vlasenko <vda linux googlemail com>]

Hello mc people,

https://savannah.gnu.org/bugs/?func=detailitem&item_id=16967

unrar of password-protected archives hangs (unrar opens
/dev/tty and sits there, waiting for the password)
The patch adds -p- switch.
A few unsafe "$var" expansions are fixed in several etxfs scripts.

Please apply the patch which is submitted there.
--
vda