Add test program fibo_call_overhead.cpp

rt/test/fibo_call_overhead.cpp

+#include <typon/core/task.hpp>
+
+#include <cstdio>
+
+using namespace typon;
+
+
+template <typename T>
+Task<typename T::promise_type::value_type> call(T task)
+{
+  co_return co_await std::move(task);
+}
+
+Task<int> fibo(int n) {
+  if (n < 2) {
+    co_return n;
+  }
+  int a = co_await call(fibo(n - 1));
+  int b = co_await call(fibo(n - 2));
+  co_return a + b;
+}
+
+int main() {
+  int result = fibo(40).call();
+  printf("%d\n", result);
+}