Merge branch 'feature/make-matrixredisttest-compile-again' into...

Merge branch 'feature/make-matrixredisttest-compile-again' into 'feature/fix-fastamg-buildhierarchy'

[matrixredistribute.hh] Fix missing #include <dune/istl/paamg/pinfo.hh>.

The previous commit made fastamg compile, but broke compilation of
matrixredisttest for me.  This makes matrixredisttest compile again.

See merge request !35