As has been discussed for a long time, decided in the December 2012
meeting, and RFCed in mid-December (#3424): we no longer build the MPI
C++ bindings by default.

The C++ bindings are still ''there'' -- starting with 1.9, we'll just
be providing a little encouragement to no longer use them.

There are no definite plans to ''remove'' the C++ bindings yet.  At
the earliest, we would remove them in the next feature series after
1.9.