scheme48 - security update

The function scheme48-send-definition in cmuscheme48.el blindly
overwrites the file /tmp/s48lose.tmp prior to sending it to the
inferior scheme process.

This action will blindly overwrite files the user has permission
to modify, causing data-loss.

For Debian 6 Squeeze, these issues have been fixed in scheme48 version 1.8+dfsg-1+deb6u1