Drop current version of Seitosh code. The contents are taken vom branch master
of [Seitosh](https://git.scc.kit.edu/Seitosh/Seitosh). The current master
commit in Seitosh is 8d7894a642.

Commands executed in the root directory of DENISE:

  rm -rfv contrib
  mkdir -pv contrib
  cp -vprd ~/git/Seitosh/src/libs/libaff contrib/aff
  cp -vprd ~/git/Seitosh/src/libs/libfourier contrib/fourier
  cp -vprd ~/git/Seitosh/src/libs/libseife contrib/libcseife
  cp -vprd ~/git/Seitosh/src/libs/libstfinv contrib/stfinv
  git add --force contrib

Since Seitosh on purpose does not provide export branches where source code
exports would be assembled in a hand-picked fashion, whole subdirectories from
Seitosh are simply copied. As a conseqeunce, the directory libcseife now also
contains Fortran code not really required by DENISE.