CPP13 — Context PIDL mapping bug

Section 1.31.3 says:

• In the C mapping, set_one_value used strings, while
  others used NamedValues containg any. Even though implementations
  need only support strings as values, the signatures now uniformly
  allow alternatives.

I would suggest to delete the entire bullet point. In particular, the notion
of allowing alternative data types as propery values for contexts doesn't
work because the receiver expects a sequence of strings with an even number
of elements; if anything but a string sequence is sent, the receiver
has no chance of unmarshaling it.

Remove bullet as suggested