Bug#986599: libmpich-dev: leaves alternatives after purge: /etc/alternatives/mpi-

[Andreas Beckmann]

Followup-For: Bug #986599
Control: severity -1 serious
Control: tag -1 patch

Actually the whole alternatives handling is missing in libmpich-dev 3.4.1-3
because the maintainer scripts are not generated correctly.

Fixes are pushed to git.

Andreas