Added postinst to remove symbolic links

The installation of libreoffice adds some symbolic links in the directory
/usr/share/applications which conflicts with the .desktop from LE.

The postinst script will remove them.

Signed-off-by: Klismann Smoger Mottin <ksm09@c3sl.ufpr.br>
Acked-by: Adriano da Luz <al08@c3sl.ufpr.br>