Add the MPI 2.2 MPI_Dist_graph functionality.

This patch reshape the way we deal with topologies completely. Where
our topologies were mainly storage components (they were not capable
of creating the new communicator), the new version is built around a
[possibly] common representation (in mca/topo/topo.h), but the functions
to attach and retrieve the topological information are specific to each
component. As a result the ompi_create_cart and ompi_create_graph functions
become useless and have been removed.

In addition to adding the internal infrastructure to manage the topology
information, it updates the MPI interface, and the debuggers support and
provides all Fortran interfaces.