Tainted computations

RLBox does not permit some operations on tainted values for safety reasons

• Using a tainted<unsigned int> to index an array in the host, i.e., int[]. This can lead to an out of bounds array access if allowed.
• Branching on tainted values. How to handle this is covered in more detail in the chapter on tainted branching.
• Comparison on the result of dereferencing a tainted pointer. This produces a tainted_bool_hint as discussed in the chapter on tainted branching.