CONFIG: update MPICH and MVAPICH versions/rules
- Note: mpich now builds libmpi.so instead of libmpich.so - define both -DMPICH_SKIP_MPICXX and -DOMPI_SKIP_MPICXX regardless of using openmpi or mpich. This simplifies the files and does not harm.
- Note: mpich now builds libmpi.so instead of libmpich.so - define both -DMPICH_SKIP_MPICXX and -DOMPI_SKIP_MPICXX regardless of using openmpi or mpich. This simplifies the files and does not harm.