* gnu/packages/patches/dealii-mpi-deprecations.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/maths.scm (dealii)[source]: Upgrade to 9.0.1. Use patch.
[arguments]: Use new MPI configuration flags.
* gnu/packages/patches/scalapack-blacs-mpi-deprecations.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/maths.scm (scalapack)[source]: Use it.
* gnu/packages/patches/superlu-dist-fix-mpi-deprecations.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/maths.scm (superlu-dist)[source]: Use it.
* gnu/packages/maths.scm: (maxima): Patch hardcoded paths.
[arguments]: Add the phase 'patch-paths' to replace references to sed,
dirname, and head with direct references to the store.
[inputs]: Add sed.