Fixed an integer overflow problem.
void *jas_calloc(size_t num_elements, size_t element_size)
{
	void *ptr;
	size_t size;
	if (!jas_safe_size_mul(num_elements, element_size, &size)) {
		return 0;
	}
	if (!(ptr = jas_malloc(size))) {
		return 0;
	}
	memset(ptr, 0, size);
	return ptr;
}

void *jas_calloc(size_t num_elements, size_t element_size)
{
	void *ptr;
	size_t size;
	if (!jas_safe_size_mul(num_elements, element_size, &size)) {
		return 0;
	}
	if (!(ptr = jas_malloc(size))) {
		return 0;
	}
	memset(ptr, 0, size);
	return ptr;
}
