Revert "[common.disable_warnings] add -Wunused-local-typedefs to clang"

Clang does not know this feature.

This reverts commit 342c6e5d660afc0fe1488fc2701b3cce010a3025.
[la.solver.istl] clean up the amg
* reorder parallel/sequential variants to share as much as possible
* default to no output