Fixed linker bug.
Fixed linker bug.

There were undefined references to 'floor' and 'log10', as the PnMPI debug
module was not linked to libm.

RWTH-HPC/PnMPI,RWTH-HPC/PnMPI,RWTH-ELP/PnMPI,RWTH-HPC/PnMPI,RWTH-ELP/PnMPI,RWTH-ELP/PnMPI