Fix an instantiation bug with nested generic lambdas and conversion to fptrs.

This patch fixes the typelocs of the conversion-operator and the conversion-operator-name and adds the parameters of the call operator to the FunctionProtoTypeLoc of the respective entities. Thus, when the template declarations (conversion operators) undergo deduction and instantiation/transformation/substitution - they add themselves to the local instantiation scope if needed.

This patch supports the following:

auto L = [](auto b) {
  return [](auto a) ->decltype(a) { return a; };
};
int (*fp)(int) = L(8);

Richard LGTM'd this patch: http://llvm-reviews.chandlerc.com/D1831

Thanks!