MPC 4.2.0 Release

MPC Release 4.1.0

- Active Message engine based on libffi
- `PRRTE` implement support for the PMIx standard runtime.
- Add libfabric support (OFI)
- Add new configuration system inside MPC (only at runtime)
- Autopriv dependency has been renamed to mpc-compiler-additions
- Add OMP 5.0 memory management support (includes HWLOC 2+ support)
- Move to HWLOC 2+
- MPIT rewrite mirroring the new configuration system
- Full communicator / Group system rewrite
- MPI 4.0 Split topology support
- Collective factorization and rewrite
- Bugfix on persistent collectives
- Expose MPC's modularity in PKGCONFIG / CMAKE
- Improved DNS resolution for TCP
- Topological collectives support
- Move to mpc-compiler-additions 0.7.0 with GCC 10.2.0
- Workshare support
- OMPT improvements
- General bugfixes and documentation

MPC-4.0.0 Beta Release

**This is a BETA release**

For this release MPC has undergone a massive refactoring. It is in some aspects not compatible with previous versions of MPC. It should bring several enhancements in terms of installation process and modularity. One should not expect binary compatibility with a previous version of MPC. Due to the massive changes, this changelog cannot be fully exhaustive.

MPC is now modular and comes in several components:

- `lowcomm` : component handling and providing the networks interfaces
- `threads` : component handling and providing the user-level thread scheduler
- `mpi` : component handling and providing the MPI standard API
- `mpiio` :  component handling and providing the IO part of the MPI standard API
- `openmp` :  component handling and providing the OpenMP standard API
- `fortran` : component handling and providing the Fortran interface for the above parallel programming APIs
- ... and other internal components

Such aforementioned components can be enabled and disabled using `--enable/disable-XX` as mpc-options in the installation script, or through variants in the new Spack building recipe.
Note that some components are dependent and cannot be installed if the dependencies are disabled (e.g., `mpiio` depends on `mpi`, and cannot be installed if `mpi` is disabled).

- **PMIX**: PMIX is now supported through `--with-pmix`
- **PRIV**: Support for new GCCs (using now external autopriv) up to 10.2.0 (using `--gcc-version=X.X.X`)
- **STATUS**: the `mpc_status` command can be used to print current MPC configuration
- **BUILD**: once installed with `./installmpc` MPC can be reconfigured with `./reconfigure` in the build directory. MPC is now longer in an `mpcframework` subdirectory

- **BUILD**: Installation process compatible with Spack to manage package dependencies
- **BUILD**: MPC now relies on autotools as its build system
- **BUILD**: It is possible to directly call `./configure` to use MPC in a modular way
- **DEPS**: dependencies can be downloaded on demand, a `light` version is a version not providing the dependencies. `./installmpc --download-missing-deps` can be used to retrieve the dependencies for a given configuration. Conversely a `full` version includes all dependencies for the default configuration
- **COMM**: communicator management was fully rewritten. The MPI_Comm is now a pointer (instead of an integer)
- **MPCRUN**: mpcrun has been fully rewritten
- **MPIIO**: MPI-IO support (ROMIO) is now integrated in MPC
- **FORTRAN**: the Fortran interface is now external and optional (MPC_Fortran)

- **mpcrun**: several options from `mpcrun` were deprecated they should now be no-op
- **installmpc**: several options from `./installmpc` were deprecated they should now be no-op

- **mpc_compiler_manager**: the `mpc_compiler_manager` command is no longer provided. MPC is now compiled against a **single** compiler
- **mpc_icc** and compiler specific wrappers: MPC now provides only `mpc_{cc,cxx,f77}` and `mpi{cc,cxx,f77}` wrappers
- **PRIV**: all privatization has been externalized in **autopriv**, including, compilers, plugins, TLS library and privatized getopt

- **COMM**: Default communicator attributes were fixed (APP_NUM, MPI_IO, MPI_HOST)
- **COLL**: fixed several collectives
- **COMM**: Major fixes in communicator management (free, creation and reuse)
- **MISC**: less contention on large SMP (various optimizations)
- **MISC**: various fixes in the lowcomm and MPI layers

New MPC Release 3.4.0, including:

MPI: optimization and corrections of NBCs, and virtual topology bugfix
OpenMP: improved OMPT support and tasks with dependencies bugfix
Net: MPI HW-enabled operation through Portals4 driver
Priv: GCC 7.3.0 as default privatizing compiler
AM: Support of custom Active Message
Doc: new markdown structure and new changelog file

MPC Release 3.3.1

Changelog:

Optimizations:
* Message latency
* Message progress with copy engine

Bugfixes
* MPI wrapper (mpirun)
* NBCs, Collectives, Communicators
* General source-code cleanup

Release Candidate for MPC 3.3.1

Contains a lot of fixes, mainly around compilation warnings.

MAIN: Update version + mailmap

Update version name

Change version for MPC 3.1

Version 3.0.0