In this assignment, you will modify your arguement broadcast routine to
communicate different datatypes by using MPI_Pack and MPI_Unpack.
<P>
Have your program read an integer and a double-precision value from standard
input (from process 0, as before), and communicate this to all of the other
processes with an MPI_Bcast call.  Use MPI_Pack to pack the data into a buffer
(for simplicity, you can use <CODE>char packbuf[100];</CODE> but consider how
to use MPI_Pack_size instead).
<P>
Note that MPI_Bcast, unlike MPI_Send/MPI_Recv operations, requires that
exactly the same amount of data be sent and received.  Thus, you will need to
make sure that all processes have the same value for the <CODE>count</CODE>
argument to MPI_Bcast.
<P>
Have all processes exit when a negative integer is read.
