warnings in tests on Windows with VS 32 bits

just for your information : when looking at the output of tests of graphenes for VS 32 bits, i've seen

```
../subprojects/mutest/tests/types.c(24): warning C4312: 'type cast': conversion from 'unsigned int' to 'void *' of greater size
../subprojects/mutest/tests/types.c(30): warning C4312: 'type cast': conversion from 'unsigned int' to 'void *' of greater size
```