Revert "[config.opts] disable warnings"

This reverts commit 460a5158a56b15e6128bd15793746861d3f42d48.
[dune-stuff] updated master
[dune-pymor] updated master
[git] ignore dirty submodules
[dune-stuff] updated master
[pymor] updated master
[dune-stuff] update container-revamp
[dune-pymor] update master