FIX: Portability of XOR32 Implementation To The ARM Platform

The xor32 implementation in the `Xor32Detector` was taking a `char` as input parameter. It turns out that the C standard does not define the 'signed-ness' of `char` leading to unportable code. (x86 interprets `char` as a `signed char` whereas ARM takes it as an `unsigned char`). This fixes this ambiguity by changing the input parameter of xor32 to `unsigned char` with the expense of a changed behaviour on x86.

**Note:** This already contains a fix to the directly affected unit tests but it breaks others as well.