[SM-I18N] Polish translation update

[Andrzej P. <kom...@us...>]

Hi,

Please find enclosed the Polish translation of the strings for
squirrelmail and plugins.

All of them are in UTF-8 (before ISO-8859-2). So all plugins have been
converted. I'm attaching sec_remove_pl_PL.png and help files in UTF-8,
also.

-- 
Regards,
Andrzej Pruszyński