* apt-pkg/algorithms.cc:

* apt-pkg/algorithms.cc:
  - let the problem resolver install packages to fix or-groups
    as a needed remove nuked another or-member (helps for #591882)

The resolver sometimes need to break or-groups because he need to
remove the previous satisfier as a result of a breaks/conflicts.
In such broken or-groups he now tries to install a non-installed
non-deleted member of the or-group to statisfy it again.
This move is dangerous as it introduces the possibility of a
bunch of "new" broken breaks/conflicts on the new statisfier or
its dependencies and we don't know about them beforehand.
We also don't have the infrastructure to undo the decision later,
so we just do it and pray!

For now a test option is provided to disable this behavior on the
fly to test if the situation is worse: pkgProblemResolver::FixByInstall