Wrong type for a sum : Int -> unsigned int

[rubeecube]

Hi

In the following code:
https://github.com/XMSS/xmss-reference/blob/171ccbd26f098542a67eb5d2b128281c80bd71a6/wots.c#L85C5-L85C5

The types of variables for the following contains both signed and unsigned int:

• params->wots_w: unsigned int
• csum: int
• msg_base_w: const int*

This might cause issues in corner cases.

1. Should csum / msg_base_w be unsigned?
2. Should csum be verified to be positive before the bitshift?