IBM 4.0 and data-check

The data-check compile-time option seems poorly debugged.

To reproduce:

1. Compile IMB-MPI1 with data-check enabled (-DCHECK)

2. Create a msg_lengths file (for L in `seq 0 100`; do echo $L >> msg_len.txt; done)

3. Run with your favorite MPI implementation using two processes, the simples possible way, with the following arguments to IMB-MPI1: 

   -msglen msg_len.txt -iter 1 Exchange

and terrible things happens.

For example, with Open MPI and the command line:

mpirun -np 2 --mca btl self,sm ./IMB-MPI1 -msglen msg_len.txt -iter 1 Exchange

I get:

mpirun noticed that process rank 1 with PID 17473 on node x.y.z  exited on signal 11 (Segmentation fault).