model-checker : update tesh for jenkins (memory management seems different between ubuntu and debian)
Add test for mpi alltoallv
Add mpi alltoallv pairwise
Add mpi alltoallv bruck and fix mpi alltoallv pairwise
Disable stream buffer when reading /proc/self/maps.

I don't fully  understand why it is necessary but, without this change, the MC
tests may terminate on a SIGSEGV.  It is likely because some memory regions are
unmapped on fclose, and then the real memory map is different from the
informations that were read.