Use of int instead of MMG5_int

Mmg handles 64-bit integers while ParMmg doesn't, e.g.,
```
int MMG3D_Get_meshSize(MMG5_pMesh mesh, MMG5_int* np, MMG5_int* ne, MMG5_int* nprism,
```
vs.
```
int PMMG_Get_meshSize(PMMG_pParMesh parmesh,int *np,int *ne,int *nprism,int *nt,
```