dns/dnsdist: unbreak build with clang 4.0
ext/json11/json11.cpp:153:24: error: invalid operands to binary expression
('nullptr_t' and 'nullptr_t')
return m_value < static_cast<const Value<tag, T> *>(other)->m_value;
~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ext/json11/json11.cpp:209:5: note: in instantiation of member function
'json11::Value<json11::Json::Type::NUL, nullptr_t>::less' requested here
JsonNull() : Value(nullptr) {}
^PR: 216069
Reported by: jbeich
Obtained from: upstream
MFH: 2017Q1