Merge branch 'master' into core-updates

gnu: openmpi: Add memchecker support.

* gnu/packages/mpi.scm (openmpi) [inputs]: Add valgrind.  Unpropagate
  gfortran.  [arguments]: Add configure flags for memchecker.

gnu: openmpi: Use our hwloc.

* gnu/packages/mpi.scm (hwloc): Propagate numactl.
  (openmpi)[inputs]: Add hwloc.
  [native-inputs]: Add pkg-config.
  [argument]: Add hwloc configure flags.

gnu: Add hwloc.

* gnu/packages/mpi.scm (hwloc): New variable.
  (openmpi): Add TODO comment.

gnu: openmpi: Fix typo in download uri

* gnu/packages/mpi.scm (openmpi)[origin]: Fix typo.

gnu: openmpi: Avoid "open source" verbiage

* gnu/packages/mpi.scm (openmpi)[synopsis,description]: Remove mention
  of "open source".

gnu: Add OpenMPI

* gnu/packages/mpi.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.