Add int_p (integer kind for populations) to hdf5_kinds_t.
Add int_p (integer kind for populations) to hdf5_kinds_t.

It's more convenient to know it (for minimal time/storage costs) rather
than check each time if int_p is 32-bit or 64-bit.

hande-qmc/hande,hande-qmc/hande,ruthfranklin/hande,hande-qmc/hande,hande-qmc/hande,hande-qmc/hande