FindMPI: Documentation and MPIEXEC improvements
This MR
- modernizes the documentation of FindMPI to current standards
- corrects the default flag for
MPIEXEC_NUMPROC_FLAG
from-np
to-n
, which is the flag given by the MPI standard, that any implementation having an mpiexec program must implement. - Documents
MPIEXEC_MAX_NUMPROCS
and makes it default to the number of processors of the host instead of the hardcoded value2
. This way it's useful in some sense and can be used for CTest and the likes.