cpp_longlong, cpp_ulonglong and c_long_double

[John-Colvin]

I presume the work in https://github.com/dlang/druntime/blob/master/src/core/stdc/config.d exists for a reason and it would be worth using those instead of hardcoding e.g. long long to long like is current done in dpp2.translation.type.translate and dpp.translation.type.translators.