All routines have two entry points: MPI_... and PMPI_....
This makes it easy to provide a single level of low-overhead routines
to intercept MPI calls without any source code modifications.
Used to provide ``automatic'' generation of trace files.
static int nsend = 0;
int MPI_Send( start, count, datatype, dest, tag, comm )
{
nsend++;
return PMPI_Send( start, count, datatype, dest, tag, comm )
}