add no_textsub.cc

day3/examples/no_textsub.cc

+template <unsigned N> constexpr unsigned fact = N * fact<N-1>;
+template <> constexpr unsigned fact<0> = 1U;
+static_assert(fact<7> == 5040);
+template <class A, class B>
+constexpr auto are_same = false;
+template <class A>
+constexpr auto are_same<A, A> = true;
+//static_assert(are_same<int, unsigned int>);
+using Integer = int;
+static_assert(are_same<int, Integer>);
+auto main() -> int {}
+