Tweak MUMPS parameter via PETSc to avoid memory error in LU factorisation.
Fix build error.
Merge remote-tracking branch 'origin/garth/clang-fixes' into garth/mumps-parameter-for-bcs-demo
Demo fix for when PETSc is not installed.
Fix MPI namespave ambiguity.
Merge branch 'garth/mumps-parameter-for-bcs-demo'