a new mpiimport extension

This extension broadcasts file contents of modules to ranks.
The ranks then save the file content to /tmp (which are local to computing
nodes)

It has a minimal MPI binding (wrapping MPI_Bcast) that works fine with mpi4py.

The goal is to minimze the number of modules loaded before mpiimport is loaded.

always run with

python -S

and add

import mpiimport;mpiimport.install()

before importing any modules. (see test.py)