Changeset baee38d in git

Remove any old cad3d.exe from a previous install

Innosetup doesn't uninstall the old version, it just overwrites it
with the new version. In 1.2.35 cad3d.exe was replaced with
survexport.exe, but a user upgrading from an older version would
still have cad3d.exe from that old version. Now we remove it to
avoid confusion.