MPI build incompatible with 64 bits integer from petsc

Created by: acrovato

CUPyDO cannot be built with MPI support on systems where 64 bits libraries (usually BLAS and LAPACK) are installed. Petsc has datatypes (eg. PetscInt) to automatically link to either 32 or 64 bits libs, but it seems that regular datatypes (eg int) have been used in CUPyDO.