API inconsistency: some SUNDIALS "Space" functions use `sunindextype` and some use `long int`

[balos1]

For example, we have

N_VSpace(N_Vector x, sunindextype *lenrw, sunindextype *leniw);
SUNMatSpace(SUNMatrix A, long  int *lenrw, long int *liniw);

[balos1]

This is sort of related to conversation in #409. We use long in many places where we should now switch to either long long or a fixed-width type like int64_t since we are now requiring C99. However, in this case I think we want to use sunindextype.

[gardner48]

The use of sunindextype in N_VSpace was an erroneous change when sunindextype was added. It would be good to address in 7.0 (at least for consistency).

[balos1]

Looks like sunindextype is used for ARKodeButcherTable_Space too.

[balos1]

This was fixed in 7.0

[balos1]

Actually, I was mistaken, this was not fixed in 7.0.0