[linear] Fix missing includes

dumux/linear/amgparallelhelpers.hh

@@ -27,6 +27,7 @@
 
 #include <dune/geometry/dimension.hh>
 #include <dune/grid/common/datahandleif.hh>
+#include <dune/grid/common/partitionset.hh>
 #include <dune/istl/owneroverlapcopy.hh>
 #include <dune/istl/paamg/pinfo.hh>
 #include <dumux/common/properties.hh>

dumux/linear/scotchbackend.hh

@@ -31,6 +31,9 @@
 #include <iostream>
 
 #if HAVE_PTSCOTCH
+#if HAVE_MPI
+#include <mpi.h>
+#endif
 extern "C"
 {
 #include <stdint.h>