misc/swissfileknife: the port had been updated to version 2.0.0.2

The `ChangeLog' accidentally appears empty in this release, will be
fixed in the next one. For now, use the `changes.txt' file instead
since we do not want to download the fixed tarball from alternative
location which does not have the benefits of SourceForge.net's vast
selection of mirrors.

Upstream bug: https://sourceforge.net/p/swissfileknife/bugs/56/