Validating Benchmarks with MPI Native implementations

[Yiltan]

Current issues:

-- the prototype used for MPI_Pready() and MPI_Parrived() is wrong.
In their parameter list, requests should be MPI_Request, not
MPI_Request*.

-- files normal_distribution.cpp and util.c do not agree on the
prototype for get_random_normal_number(). In one case, the function
takes two parameters; in the other, none.

-- if we follow the instructions in the README (CC=mpicc), compilation
of the C++ file fails. However, if I switch compilation to CC=mpicxx, C
files do not compile because they use constructions forbidden in C++.

-- for linking, -lm is missing (needed by the call to sqrt).