update gitignore and changelog
fix compilation without mpich3 testsuite
Add preliminary support for MPI_Pack, MPI_Pack_size, and MPI_Unpack.
Activate tests for these functions. Somes cases with too complex imbricated datatypes are not supported (yet).
changelog update
fix the tesh of one last command

Thanks adsein for all your great work on these points.
Merge branch 'master' of scm.gforge.inria.fr:/gitroot/simgrid/simgrid
clean after augustin ;)