few more docs

Hi,

although I might touch these sources again tomorrow, I thought it's good to open a PR in order to receive early feedback (mostly of crude type about missing pieces/paragraphs). Yet, any feedback is welcome :)

tia, F.
I would create a list with three items:

 * various compilers, including GCC, Intel, Clang, CUDA
 * common MPI libraries, such as Intel MPI, MPICH, MVAPICH2, OpenMPI
 * various numerical libraries, including ATLAS, Intel MKL, OpenBLAS, ScalaPACK, FFTW