vici: Don't include-depend on libstrongswan for boolean types

vici: Don't include-depend on libstrongswan for boolean types

As we want to avoid the libstrongswan include dependencies for libvici, avoid
the use of the bool type. Unfortunately this change may break the ABI for
vici_dump(). As this function is mostly for debugging purposes, we do it
nonetheless; my apologies if somebody already relies on the ABI stability of
that function.