Add a check for mpi4py version during Cython compilation.

Version 2 of mpi4py has changed the name of a submodule from mpi_c to
libmpi. We need to check which one to use at compile time.

This directory contains mpi4py-independent Python code for MUSIC library
configuration.  It is used by the PyNN/MUSIC interface.

Possibly this code should eventually be integrated into pymusic.

newer versions of mpi4py.

not released version
SVN: multiconn@1048