Casting between `int64_t *` and `int32_t *` does *not* maintain the values in
the array. Instead, it tells the compiler to interpret the memory at that
pointer as an array of a different type (i.e., two `int32_t` elements "become"
one `int64_t` element). That can lead to all kinds of errors and is very not
what was intended.

Remove the integer pointer casts to allow the compiler to emit an error on
compile-time instead of potentially causing, e.g., an array overflow on
runtime if `sunindextype` has a different size from `KLU_INDEXTYPE`.

Signed-off-by: Markus Mützel <[email protected]>

…type

If `sunindextype` is a 64-bit integer, `SuiteSparse_long` must also be a
64-bit integer or KLU cannot be used.
Add a CMake check to fail during configuration if the sizes don't match.

Signed-off-by: Markus Mützel <[email protected]>