Two external MPI libraries are now created: libmpi.la and libmpi_abi.la.
Backend code that was originally in libmpi.la has been extracted into
libopen-mpi.la to be linked into both libraries.

Parts of the Open MPI C interface are now being generated by a python
script (abi.py) from modified source files (named with *.in). This
script generates files for both the ompi ABI and the standard ABI from
the same source file, also including new bigcount interfaces.

To compile standard ABI code, there's a new mpicc_abi compiler wrapper.
The standard ABI does not yet include all functions or symbols, so more
complicated source files will not compile. ROMIO must be disabled for
the code to link, since it's relying on the external MPI interface.

Signed-off-by: Jake Tronge <[email protected]>

Signed-off-by: Jake Tronge <[email protected]>

Signed-off-by: Jake Tronge <[email protected]>

If the ABI source files have not been generated, then Python >=3.6 is
required. ABI source file generation is turned on by default as long as
the proper Python is found. The standard ABI library will only be built
with '--enable-standard-abi'.

Signed-off-by: Jake Tronge <[email protected]>

Signed-off-by: Jake Tronge <[email protected]>