MPI support relies on removed C++ bindings

[lexming]

There are 3 points in input.C where MPI is handled through its C++ bindings. These can be found at lines 1932, 2304 and 2694 and they all perform a very similar broadcast. The snippet of the first one follows:

StackBlock/input.C

Lines 1932 to 1944 in f95317b

	#ifndef SERIAL
	MPI::COMM_WORLD.Barrier();
	long intdim = oneIntegralMem+twoIntegralMem;
	long maxint = 26843540; //mpi cannot transfer more than these number of doubles
	long maxIter = intdim/maxint;
	for (int i=0; i<maxIter; i++) {
	MPI::COMM_WORLD.Bcast(v1.set_data()+i*maxint, maxint, MPI_DOUBLE, 0);
	MPI::COMM_WORLD.Barrier();
	}
	MPI::COMM_WORLD.Bcast(v1.set_data()+(maxIter)*maxint, oneIntegralMem+twoIntegralMem - maxIter*maxint, MPI_DOUBLE, 0);
	MPI::COMM_WORLD.Barrier();
	#endif

The issue is that the C++ bindings were deprecated in MPI 2.2 (almost 10 years ago) and removed in MPI 3.0, which makes StackBlock very difficult to compile in a modern MPI stack. Since StackBlock already uses Boost:MPI to leverage most of its MPI communications, the solution would be to move these 3 broadcast to Boost:MPI as well and delete the include on mpi.h altogether.