Blender Git Loki

Fix integer overflow in BLI_mempool_as_arrayN()

`(size_t)(int * int)` will actually cast overflown integer to size_t,
which isn't what was intended here. Correct thing would be to cast
in the following manner `(size_t)int * int`.

In this particular case can as well use function which is designed to
allocate an array of memory without overflow.