#10 check for password protected files on double click

[Markus Koschany]

You can view content of files if you double-click on them in xarchiver's
treeview. This patch checks for password protected files which cannot be
viewed unless the password has been provided by the user.

If no valid password is detected, xarchiver will refuse to display files, which
otherwise could result in a complete freeze of the application.

Bug: http://bugs.debian.org/633598

[Markus Koschany]